The high-pressure structural and elastic properties of ${\mathrm{MgCO}}_{3},{\mathrm{CaCO}}_{3}$, and $\mathrm{MgCa}{\left({\mathrm{CO}}_{3}\right)}_{2}$ have been investigated with density functional theory. By computing the isotropic elastic constants, we found that the bulk and shear acoustic wave velocities are smaller in carbonates than in their respective silica…

[Phys. Rev. B 94, 104112] Published Fri Sep 23, 2016

]]>We study the effect of electronic Coulomb correlations on the vacancy formation energy in paramagnetic $\alpha \text{\u2212}\mathrm{Fe}$ within *ab initio* dynamical mean-field theory. The calculated value for the formation energy is substantially lower than in standard density-functional calculations and in excellent agreement w…

[Phys. Rev. B 94, 100102(R)] Published Wed Sep 21, 2016

]]>Shock compression of silicon (Si) under extremely high pressures (>100 Mbar) was investigated by using two first-principles methods of orbital-free molecular dynamics (OFMD) and path integral Monte Carlo (PIMC). While pressures from the two methods agree very well, PIMC predicts a second compression …

[Phys. Rev. B 94, 094109] Published Thu Sep 15, 2016

]]>We present an experimental and theoretical study of the optically detected magnetic resonance signals for ensembles of negatively charged nitrogen-vacancy (NV) centers in a ${}^{13}\mathrm{C}$ isotopically enriched single-crystal diamond. We observe four broad transition peaks with superimposed sharp features at ze…

[Phys. Rev. B 94, 094108] Published Wed Sep 14, 2016

]]>Accelerated molecular dynamics reveals a mechanism transition and strong temperature dependence of dislocation nucleation from grain boundaries (GBs) in Cu. At stress levels up to $\sim 90\%$ of the ideal dislocation-nucleation stress, atomic shuffling at the $E$ structural unit in a GB acts as a precursor t…

[Phys. Rev. B 94, 104110] Published Wed Sep 14, 2016

]]>High-temperature atomic configurations of fcc Fe-Cr-Ni alloys with alloy composition close to austenitic steel are studied in statistical thermodynamic simulations with effective interactions obtained in *ab initio* calculations. The latter are done taking longitudinal spin fluctuations (LSF) into con…

[Phys. Rev. B 94, 104111] Published Wed Sep 14, 2016

]]>Using an experimental setup designed to scan a submicron sized light spot and collect the photogenerated current through larger electrodes, we map the photovoltaic response in ferroelectric $\mathrm{BiFe}{\mathrm{O}}_{3}$ single crystals. We study the effect produced by a unique 180° ferroelectric domain wall (DW) and show …

[Phys. Rev. B 94, 094107] Published Mon Sep 12, 2016

]]>Diffusionless displacive lattice rearrangements, which include martensitic transformations, are in real materials often accompanied by a displacive drag of interstitials. The interplay of both processes leads to a particular atomistic arrangement of the interstitials in the product phase, which is d…

[Phys. Rev. B 94, 104109] Published Mon Sep 12, 2016

]]>Two-dimensional (2D) ${\mathrm{BNSi}}_{2}$ has been recently proposed to be a viable candidate material with a graphenelike structure. We have carried out *ab initio* evolutionary ground state searches and uncovered a number of 2D structures in the $\left(\mathrm{BN}\right){}_{x}{\mathrm{Si}}_{1-x}$ pseudobinary system with considerably lower energies. Neve…

[Phys. Rev. B 94, 094105] Published Fri Sep 09, 2016

]]>We explore topological transitions in parameter space in order to enable adiabatic passages between regions adiabatically disconnected within a given parameter manifold. To this end, we study the Hamiltonian of two coupled qubits interacting with external magnetic fields, and make use of the analogy…

[Phys. Rev. B 94, 094106] Published Fri Sep 09, 2016

]]>In this work, a systematic investigation of the alloying behavior on the $M$ sublattice of ${M}_{2}\mathrm{AlC}$, where $M$ is Ti, V, Zr, and Hf with elements in the first transition metal row as well as Ca and Sc is carried out via a combination of alloy theoretic approaches and density functional theory for 41 alloy …

[Phys. Rev. B 94, 104106] Published Fri Sep 09, 2016

]]>The role of quantum ion dynamics in the low melting temperatures of Li is investigated from first principles theory. Free energies of solid and liquid phases are obtained at the classical and quantum ion levels. The results are used to determine the Li melting curve in the 40–60 and 110–150 GPa pres…

[Phys. Rev. B 94, 104107] Published Fri Sep 09, 2016

]]>The exceptionally large piezoelectric response of the morphotropic-phase-boundary (MPB) composition of the lead-free piezoelectric system $(1-x\left)\mathrm{Ba}\right(\mathrm{T}{\mathrm{i}}_{0.8}\mathrm{Z}{\mathrm{r}}_{0.2}){\mathrm{O}}_{3}-x\left(\mathrm{B}{\mathrm{a}}_{0.7}\mathrm{C}{\mathrm{a}}_{0.3}\right)\mathrm{Ti}{\mathrm{O}}_{3}$ has attracted great attention in recent years. Here in this paper we report a detailed investigation of the structural pha…

[Phys. Rev. B 94, 104108] Published Fri Sep 09, 2016

]]>We used *ab initio* random structure searching (AIRSS) to investigate polymorphism in ${\mathrm{C}}_{3}{\mathrm{N}}_{4}$ carbon nitride as a function of pressure. Our calculations reveal new framework structures, including a particularly stable chiral polymorph of space group $P{4}_{3}{2}_{1}2$ containing mixed $s{p}^{2}$ and $s{p}^{3}$ bonding, that we ha…

[Phys. Rev. B 94, 094104] Published Thu Sep 08, 2016

]]>Ferroelectrics that allow a coupling between the polarization and another order parameter are of great interest because they could make the electric field control of nonpolar order parameters possible. In recent years, “hybrid improper’” ferroelectrics - materials where the polarization couples to two different structural distortions - have emerged as a possible way to realize this goal. Theoretical predictions of hybrid improper ferroelectricity in layered perovskite materials were followed by its first experimental realization in Ca${}_{3}$Ti${}_{2}$O${}_{7}$ in 2015. However, the precise pathway by which the polarization reverses in this material during ferroelectric switching remains an open question. The authors address this question and lay the groundwork for understanding the unexpectedly complex domain structure of Ca${}_{3}$Ti${}_{2}$O${}_{7}$, consisting of a network of multiple types of domain walls and topological defects.

[Phys. Rev. B 94, 104105] Published Thu Sep 08, 2016

]]>Spintronics holds the promise of novel functionality and higher device performance, but a massive challenge is to find semiconducting materials with good electronic properties that are also ferromagnetic. Dilute magnetic semiconductors (DMS) such as Mn-doped GaAs have great potential but are notoriously difficult to make, only stabilizing in thin films in most cases. Recently, a promising new class of DMS materials based on the chemistry and structure of iron-based superconductors has been discovered, including the compound (Ba,K)(Zn,Mn)${}_{2}$As${}_{2}$. These materials can be synthesized in bulk form, providing an unprecedented opportunity to study the mechanism of ferromagnetism in semiconductors. In this work, the authors present detailed temperature-dependent characterization of the atomic and magnetic structure of (Ba,K)(Zn,Mn)${}_{2}$As${}_{2}$ using x-ray and neutron pair distribution function techniques, establishing the existence of an unexpected structural distortion on a short length scale and surprisingly robust short-range ferromagnetic correlations that persist even at room temperature. These results fill in important gaps in the experimental understanding of DMS materials and provide valuable guidance to their theoretical description.

[Phys. Rev. B 94, 094102] Published Tue Sep 06, 2016

]]>$\mathrm{G}{\mathrm{e}}_{2}\mathrm{S}{\mathrm{b}}_{2}\mathrm{T}{\mathrm{e}}_{5}$ polycrystalline films either in the trigonal stable phase or in the metastable rock-salt structure have been irradiated with 150 keV ${\mathrm{Ar}}^{+}$ ions. The effects of disorder are studied by electrical, optical, and structural measurements and density functional theory (DFT) simulations. In the met…

[Phys. Rev. B 94, 094103] Published Tue Sep 06, 2016

]]>In general, crystallite size reduction is known to suppress the ferroic order (polarization or magnetization) in ferroelectric and magnetic systems. Using free particles of a giant tetragonality $(c/a\u20131=0.18)$ ferroelectric alloy $\mathrm{BiFe}{\mathrm{O}}_{3}\text{\u2212}\mathrm{PbTi}{\mathrm{O}}_{3}$ as the model system, here we show that the intrinsic size …

[Phys. Rev. B 94, 104104] Published Tue Sep 06, 2016

]]>Polar discontinuity at interfaces plays deterministic roles in charge transport, magnetism, and even superconductivity of functional oxides. To date, most polar discontinuity problems have been explored in heterointerfaces between two dissimilar materials. Here, we show that charged domain walls (CD…

[Phys. Rev. B 94, 100101(R)] Published Fri Sep 02, 2016

]]>Two-dimensional (2D) materials have attracted considerable interest due to their remarkable properties and potential applications for nanoelectronics, electrodes, energy storage devices, among others. However, many well-studied 2D materials lack appreciable conductivity and tunable mechanical streng…

[Phys. Rev. B 94, 104103] Published Fri Sep 02, 2016

]]>Investigation of real two-dimensional systems with Dirac-like electronic behavior under the influence of magnetic field is challenging and leads to many interesting physical results. In this paper we study a 2D graphene model with a particular form of magnetic field as a superposition of a homogeneo…

[Phys. Rev. B 94, 094101] Published Thu Sep 01, 2016

]]>The structural and electronic properties of a series of ${\mathrm{SrMnO}}_{3}$ thin films grown on different substrates leading to different biaxial strains are examined by means of aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and electron energy-loss spectroscopy (EE…

[Phys. Rev. B 94, 104101] Published Thu Sep 01, 2016

]]>Molybdenum (Mo) is a transition metal with a wide range of technical applications. There has long been strong interest in its high-pressure behavior, and it is often used as standard for high-pressure experiments. Combining powder x-ray diffraction and dynamic ramp compression, structural and equati…

[Phys. Rev. B 94, 104102] Published Thu Sep 01, 2016

]]>The family of layered ${M}_{n+1}A{X}_{n}$ compounds provides a large class of materials with applications ranging from magnets to high-temperature coatings to nuclear cladding. In this work, we employ a density-functional-theory-based discovery approach to identify a large number of thermodynamically stable ${M}_{n+\mathrm{\dots}}$

[Phys. Rev. B 94, 054116] Published Wed Aug 31, 2016

]]>Synchrotron x-ray diffraction experiments were performed on the network compounds ${\mathrm{Ba}}_{1-x}{\mathrm{Sr}}_{x}{\mathrm{Al}}_{2}{\mathrm{O}}_{4}$ at temperatures between 15 and 800 K. The ferroelectric phase of the parent ${\mathrm{BaAl}}_{2}{\mathrm{O}}_{4}$ is largely suppressed by substituting a small amount of Sr for Ba and disappears for $x\ge 0.1$. Structural refinements revea…

[Phys. Rev. B 94, 054117] Published Wed Aug 31, 2016

]]>The monoclinic (M) phases in high-performance relaxor-based ferroelectric single crystals have been recognized to be a vital structural factor for the outstanding piezoelectric property. However, due to the complexity of the structure in M phases, the understanding about it is still limited. In this…

[Phys. Rev. B 94, 054115] Published Mon Aug 29, 2016

]]>The quantum anomalous Hall effect (QAHE) originates from a combination of the spin-orbital coupling and the breaking of time-reversal symmetry due to intrinsic ferromagnetic ordering and was recently observed in Cr and V doped magnetic topological insulators (TIs). However, it was only observed at e…

[Phys. Rev. B 94, 054113] Published Fri Aug 26, 2016

]]>A recent quasielastic neutron scattering (QENS) study of hydrogen in heavily deformed fcc palladium provided the first direct measurement of hydrogen pipe diffusion, which has a significantly higher diffusivity and lower activation barrier than in bulk. While *ab initio* estimates of hydrogen diffusio…

[Phys. Rev. B 94, 054114] Published Fri Aug 26, 2016

]]>Crystal of ${\mathrm{GaV}}_{4}{\mathrm{S}}_{8}$, a multiferroic system hosting a Néel-type skyrmion lattice phase, has been investigated by polarized Raman and IR spectroscopy above and below the ferroelectric phase transition. Counts of the observed IR and Raman-active modes belonging to distinct irreducible representations agr…

[Phys. Rev. B 94, 060104(R)] Published Fri Aug 26, 2016

]]>First-principles simulations of the porous layered calcogenide materials ${\mathrm{Li}}_{2}{\mathrm{SnO}}_{3}$ and ${\mathrm{Li}}_{2}{\mathrm{SnS}}_{3}$ are used to study their structures, Li ion mobilities, and their interactions with excess Li. The pristine materials are characterized by a regular pattern of voids within the calcogenide layers which are oc…

[Phys. Rev. B 94, 064108] Published Fri Aug 26, 2016

]]>We introduce the concept of a *reflection quasilattice*, the quasiperiodic generalization of a Bravais lattice with irreducible reflection symmetry. Among their applications, reflection quasilattices are the reciprocal (i.e., Bragg diffraction) lattices for quasicrystals and quasicrystal tilings, such…

[Phys. Rev. B 94, 064107] Published Thu Aug 25, 2016

]]>The evolution of local ferroelectric lattice distortions in multiferroic ${\mathrm{Ge}}_{1-x}{\mathrm{Mn}}_{x}\mathrm{Te}$ is studied by x-ray diffraction, x-ray absorption spectroscopy, and density functional theory. We show that the anion/cation displacements smoothly decrease with increasing Mn content, thereby reducing the ferroelect…

[Phys. Rev. B 94, 054112] Published Fri Aug 19, 2016

]]>The confinement effect of intercalated atoms in van der Waals heterostructures can lead to interesting interactions between the confined atoms or molecules and the overlaying two-dimensional (2D) materials. Here we report the formation of ordered Cu(100) $p(2\times 2)$ oxygen superstructures by oxygen inter…

[Phys. Rev. B 94, 064106] Published Thu Aug 18, 2016

]]>Computationally-guided material discovery is being increasingly employed using a descriptor-based screening through the calculation of a few properties of interest. A precise understanding of the uncertainty associated with first-principles density functional theory calculated property values is imp…

[Phys. Rev. B 94, 064105] Published Tue Aug 16, 2016

]]>We study a system of particles in two dimensions interacting via a dipolar long-range potential $D/{r}^{3}$ and subject to a square-lattice substrate potential $V\left(\mathbf{r}\right)$ with amplitude $V$ and lattice constant $b$. The isotropic interaction favors a hexagonal arrangement of the particles with lattice constant $a$, wh…

[Phys. Rev. B 94, 054110] Published Mon Aug 15, 2016

]]>We present a theoretical scheme to calculate the elastic constants of magnetic materials in the high-temperature paramagnetic state. Our approach is based on a combination of disordered local moments picture and *ab initio* molecular dynamics (DLM-MD). Moreover, we investigate a possibility to enhance…

[Phys. Rev. B 94, 054111] Published Mon Aug 15, 2016

]]>We report on the six-dimensional (6D) structural refinement of three members of the i-$R$-Cd quasicrystals ($R$ = Gd, Dy, Tm) via synchrotron x-ray diffraction from single-grain samples, and show that this series is isostructural to the i-${\mathrm{YbCd}}_{5.7}$ quasicrystal. However, our refinements suggest that the $R$…

[Phys. Rev. B 94, 060103(R)] Published Mon Aug 15, 2016

]]>The light-elemental solutes B, C, N, and O can penetrate the surface of Mg alloys and diffuse during heat treatment or high temperature application, forming undesirable compounds. We investigate the diffusion of these solutes by determining their stable interstitial sites and the interpenetrating ne…

[Phys. Rev. B 94, 054106] Published Fri Aug 12, 2016

]]>An atomic interaction is identified in all perovskite compounds, such as $AB{\mathrm{O}}_{3}$ oxides, that can potentially result in unconventional structures. The term is harmonic in nature and couples the motions of the $A$ cations with the rotations of the oxygen octahedra in the perovskite lattice. When strong en…

[Phys. Rev. B 94, 054107] Published Fri Aug 12, 2016

]]>The tetragonal form of ${\mathrm{ZrO}}_{2}$ is used in a wide range of technologies. In this study, we systematically explore the effect of strain on the relative stability of symmetrically equivalent tetragonal variants of ${\mathrm{ZrO}}_{2}$ using first-principles density functional theory. We focus, in particular, on the role …

[Phys. Rev. B 94, 054108] Published Fri Aug 12, 2016

]]>Dynamic dielectric and piezoelectric constants of ferroelectrics increase proportionally to the amplitude of alternating electric field as a result of hysteretic Rayleigh-type motion of domain walls. Here a hysteresis-free quadratic field dependence of the dynamic dielectric response is experimental…

[Phys. Rev. B 94, 054109] Published Fri Aug 12, 2016

]]>We investigate the thermodynamic stability of carbon-rich icosahedral boron carbide at different compositions, ranging from ${\mathrm{B}}_{4}\mathrm{C}$ to ${\mathrm{B}}_{2}\mathrm{C}$, using first-principles calculations. Apart from ${\mathrm{B}}_{4}\mathrm{C}$, generally addressed in the literature, ${\mathrm{B}}_{2.5}\mathrm{C}$, represented by ${\mathrm{B}}_{10}{\mathrm{C}}_{2}^{p}$(C-C), where ${\mathrm{C}}^{p}$ and (C-C) denote a carbon at…

[Phys. Rev. B 94, 054104] Published Wed Aug 10, 2016

]]>We develop a phase-field model that describes the elastic distortion of a ferroelastic material with cubic anisotropy due to an arbitrary dislocation network and a uniform external load. The dislocation network is characterized using the Nye tensor and enters the formulation via a set of incompatibi…

[Phys. Rev. B 94, 054105] Published Wed Aug 10, 2016

]]>In this paper, we develop a multiscale approach to model intrinsic dissipation under high frequency of vibrations in solids. For vibrations with a timescale comparable to the phonon relaxation time, the local phonon distribution deviates from the equilibrium distribution. We extend the quasiharmonic…

[Phys. Rev. B 94, 064103] Published Wed Aug 10, 2016

]]>The pressure-temperature $\left(P\text{\u2212}T\right)$ phase diagram of ${\mathrm{N}}_{2}\text{\u2212}{\mathrm{O}}_{2}$ mixture with a composition of ${\mathrm{N}}_{2}$-48 mol % ${\mathrm{O}}_{2}$ has been investigated using x-ray diffraction and the phase stability of a hexagonal phase (space group: $P6$*/mmm*), with the kagome lattice examined under high-pressure and low-temperature conditions. Wh…

[Phys. Rev. B 94, 064104] Published Wed Aug 10, 2016

]]>Point defects in the binary group-IV monochalcogenide monolayers of SnS, SnSe, GeS, and GeSe are investigated using density functional theory calculations. Several stable configurations are found for oxygen defects, however, we give evidence that these materials are less prone to oxidation than phos…

[Phys. Rev. B 94, 054103] Published Tue Aug 09, 2016

]]>We present evidence of near-infrared photoluminescence (PL) signature of nitrogen vacancy centers ${\left({\mathrm{N}}_{\mathrm{C}}{\mathrm{V}}_{\mathrm{Si}}\right)}^{-}$ in silicon carbide (SiC). This center exhibits an $S=1$ ground state spin similar to the ${\mathrm{NV}}^{-}$ center in diamond. We have performed photoluminescence excitation measurements at cryogenic temperatur…

[Phys. Rev. B 94, 060102(R)] Published Fri Aug 05, 2016

]]>In this work, using zero kelvin *ab initio* calculations, we revisit the structure and ferroelectric phase transition in antiphase domain boundaries (APBs) in ${\text{SrTiO}}_{3}$ (STO), which has been previously addressed in terms of a phenomenological approach. We confirmed the main qualitative conclusion of the …

[Phys. Rev. B 94, 054102] Published Wed Aug 03, 2016

]]>The nitrogen-vacancy (NV) center in diamond has attractive properties for a number of quantum technologies that rely on the spin angular momentum of the electron and the nuclei adjacent to the center. The nucleus with the strongest interaction is the ${}^{13}\mathrm{C}$ nuclear spin of the first shell. Using this d…

[Phys. Rev. B 94, 060101(R)] Published Wed Aug 03, 2016

]]>${A}_{2}\mathrm{S}{\mathrm{n}}_{2}{\mathrm{O}}_{7}$ $(A=\mathrm{Nd},\text{Sm},\text{Gd},\text{Er},\text{Yb},\text{and Y})$ materials with the pyrochlore structure were irradiated with 2.2 GeV Au ions to systematically investigate disordering of this system in response to dense electronic excitation. Structural modifications were characterized, over multiple length scales, by transmission…

[Phys. Rev. B 94, 064102] Published Wed Aug 03, 2016

]]>Crystal plasticity occurs by deformation bursts due to the avalanchelike motion of dislocations. Here we perform extensive numerical simulations of a three-dimensional dislocation dynamics model under quasistatic stress-controlled loading. Our results show that avalanches are power-law distributed a…

[Phys. Rev. B 94, 064101] Published Tue Aug 02, 2016

]]>Structural and thermal properties of $\mathrm{BiFe}{\mathrm{O}}_{3}$ under compressive epitaxial strain are investigated using a shell model fitted to first-principles calculations. We show that a model developed for the bulk describes properly the behavior of the compound as function of the strain, including the appearance…

[Phys. Rev. B 94, 054101] Published Mon Aug 01, 2016

]]>Strain effects on epitaxial thin films of $\mathrm{LaNi}{\mathrm{O}}_{3}$ grown on different single crystalline substrates are studied by Raman scattering and first-principles simulation. New Raman modes, not present in bulk or fully relaxed films, appear under both compressive and tensile strains, indicating symmetry reduc…

[Phys. Rev. B 94, 014118] Published Fri Jul 29, 2016

]]>Scattering of photons by phonons, or Brillouin scattering, enables manipulation and control of light and has led to revolutionary applications, from slow light to saser and cooling of micromechanical resonators. Recently, enhanced light and sound interaction has been demonstrated in waveguides. Howe…

[Phys. Rev. B 94, 024115] Published Thu Jul 28, 2016

]]>By means of positron annihilation lifetime spectroscopy, we have investigated the native defects present in ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$, which belongs to the family of topological insulators. We experimentally demonstrate that selenium vacancy defects $\left({\text{V}}_{\text{Se1}}\right)$ are present in ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ as-grown samples, and that their charge …

[Phys. Rev. B 94, 014117] Published Wed Jul 27, 2016

]]>Exploration of the vast configuration space encountered in a multicomponent alloy is impossible without a suitable engine like the cluster-expansion (CE) method. While a CE ansatz can be formulated for an arbitrary number of components $n$, the combinatorial explosion of configuration space with incre…

[Phys. Rev. B 94, 014116] Published Mon Jul 25, 2016

]]>We study, by means of an atomistic toy model, the interplay of ferroelastic twin patterns and electrical polarization. Our molecular dynamics simulations reproduce polarity in straight twin walls as observed experimentally. We show, by making contact with continuum theory, that the effect is governe…

[Phys. Rev. B 94, 024114] Published Mon Jul 25, 2016

]]>Amorphous (a)-${\mathrm{HfO}}_{2}$ is a prototype high dielectric constant insulator with wide technological applications. Using *ab initio* calculations we show that excess electrons and holes can trap in a-${\mathrm{HfO}}_{2}$ in energetically much deeper polaron states than in the crystalline monoclinic phase. The electrons and h…

[Phys. Rev. B 94, 020103(R)] Published Thu Jul 21, 2016

]]>Based on first-principles phonon and finite temperature molecular dynamics calculations including spin-orbit coupling, we showed that free-standing single-layer phases of bismuth, namely buckled honeycomb and asymmetric washboard structures named as bismuthene, are stable at high temperature. We stu…

[Phys. Rev. B 94, 014115] Published Wed Jul 20, 2016

]]>Core-shell coating structures and concentration gradient materials may enhance Li-ion battery performance by integrating advantages of core and shell components without introducing unfavorable problems associated with general coatings. The fundamental thermodynamic properties of concentration gradie…

[Phys. Rev. B 94, 014114] Published Tue Jul 19, 2016

]]>Lattice defects are inevitably present in two-dimensional materials, with direct implications on their physical and chemical properties. We show that the formation energy of a lattice defect in buckled two-dimensional crystals is not uniquely defined as it takes different values for different bounda…

[Phys. Rev. B 94, 020102(R)] Published Tue Jul 19, 2016

]]>The wavelength dependence of the threshold for femtosecond optical breakdown in water provides information on the interplay of multiphoton, tunneling, and avalanche ionization and is of interest for parameter selection in laser surgery. We measured the bubble threshold from ultraviolet to near-infra…

[Phys. Rev. B 94, 024113] Published Mon Jul 18, 2016

]]>The structural evolution with pressure in bulk $\mathrm{Mo}{\mathrm{S}}_{2}$ has been investigated by high-pressure x-ray diffraction using synchrotron radiation. We found that the out-of-plane S-Mo-S bond angle θ increases and that in in-plane angle $\varphi $ decreases linearly with increasing pressure across the known semiconduct…

[Phys. Rev. B 94, 020101(R)] Published Fri Jul 15, 2016

]]>We report synchrotron x-ray diffraction investigations of interfacially engineered oxygen octahedral rotations and their impact on strain relief in perovskite $\mathrm{SrRu}{\mathrm{O}}_{3}$ films. We show that octahedral rotations with distinct patterns and magnitudes can be accommodated into coherently grown films. The $\mathrm{Sr\dots}$

[Phys. Rev. B 94, 024112] Published Fri Jul 15, 2016

]]>Icosahedral quasicrystals (IQCs) with extremely high degrees of translational order have been produced in the laboratory and found in naturally occurring minerals, yet questions remain about how IQCs form. In particular, the fundamental question of how locally determined additions to a growing clust…

[Phys. Rev. B 94, 014113] Published Thu Jul 14, 2016

]]>We discuss a fundamental theory of how to calculate the phonon-loss sector of the energy-loss spectrum for electrons scattering from crystalline solids. A correlated model for the atomic motion is used for calculating the vibrational modes. Spectra are calculated for crystalline silicon illuminated …

[Phys. Rev. B 94, 014110] Published Wed Jul 13, 2016

]]>Many earlier high-resolution x-ray studies of criticality seemingly invalidated the single-length scaling hypothesis that is predicted by the three-dimensional Ising model, a cornerstone in the theory of critical phenomena. Speculations about the reasons for these discrepancies have concentrated on the role of impurities and on surface-induced strain in the crystalline samples. The general validity of the Ising model for real systems has also been questioned. Here, the authors present x-ray scattering data on the temperature-induced order-disorder transition in $\beta $-brass, nature’s archetypical realization of the Ising model. These investigations unambiguously show that the Ising model does precisely describe the critical behavior observed and, in particular, that the short-range order parameter indeed exhibits single-length scaling. The surface sensitivity has been varied in the experiments without any substantial differences observed.

[Phys. Rev. B 94, 014111] Published Wed Jul 13, 2016

]]>The pressure evolution of the local structure of ${\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ hematite has been determined by extended x-ray absorption fine structure up to $\sim 79$ GPa. Below the phase-transition pressure at $\sim 50$ GPa, no increasing of ${\mathrm{FeO}}_{6}$ octahedra distortion is observed as pressure is applied. Above the phase transition, an…

[Phys. Rev. B 94, 014112] Published Wed Jul 13, 2016

]]>Interatomic interactions and ordering in fcc Ni-rich Ni-Re alloys are studied by means of first-principles methods combined with statistical mechanics simulations based on the Ising Hamiltonian. First-principles calculations are employed to obtain effective chemical and strain-induced interactions, …

[Phys. Rev. B 94, 024111] Published Wed Jul 13, 2016

]]>We perform density functional calculations to investigate the structure of the intermetallic alloy FeRh under epitaxial strain. Bulk FeRh exhibits a metamagnetic transition from a low-temperature antiferromagnetic (AFM) phase to a ferromagnetic phase at 350 K, and its strain dependence is of interes…

[Phys. Rev. B 94, 014109] Published Tue Jul 12, 2016

]]>In 1949, Forsbergh, Jr. reported spontaneous spatial ordering in the birefringence patterns seen in flux-grown $\mathrm{BaTi}{\mathrm{O}}_{3}$ crystals under the transmission polarized light microscope [Phys. Rev. **76**, 1187 (1949)]. Stunningly regular square-net arrays were often only found within a finite temperature window…

[Phys. Rev. B 94, 024109] Published Tue Jul 12, 2016

]]>The phenomenon of self-organization of domains into a “square-net pattern” in single-crystal, flux-grown $\mathrm{BaTi}{\mathrm{O}}_{3}$ several degrees below the ferroelectric to paraelectric phase transition was investigated using *in situ* synchrotron x-ray topography. The tetragonal distortion of the crystal was determine…

[Phys. Rev. B 94, 024110] Published Tue Jul 12, 2016

]]>We present a scanning tunneling microscopy (STM) study of the domain evolution across two first-order phase transitions of stripe modulations in ${\mathrm{IrTe}}_{2}$ that occur at ${T}_{\mathrm{C}}\approx 275$ K and ${T}_{\mathrm{S}}\approx 180$ K, respectively. Phase coexistence of the hexagonal $(1\times 1)$ structure and the $(5\times 1)$ stripe modulation is observed at ${\dots}_{}$

[Phys. Rev. B 94, 014106] Published Mon Jul 11, 2016

]]>At variance with structural ferroic phase transitions which give rise to macroscopic tensors coupled to macroscopic fields, criteria defining antiferroelectric (AFE) phase transitions are still under discussion due to the absence of specific symmetry properties characterizing their existence. They a…

[Phys. Rev. B 94, 014107] Published Mon Jul 11, 2016

]]>Current materials-related calculations employ density-functional theory (DFT), commonly using the (semi-)local-density approximations for the exchange-correlation (xc) functional. The difficulties in arriving at a reasonable description of van der Waals (vdW) interactions by DFT-based models is to d…

[Phys. Rev. B 94, 024108] Published Mon Jul 11, 2016

]]>We study the temperature-dependent evolution of the octahedral tilt order in a lead-free relaxor ferroelectric and its impact on the ferroelectric properties. Using diffuse neutron scattering on a $0.964{\mathrm{Na}}_{1/2}{\mathrm{Bi}}_{1/2}{\mathrm{TiO}}_{3}\text{\u2212}0.036{\mathrm{BaTiO}}_{3}$ single crystal, we suggest a model for the temperature-dependent nanost…

[Phys. Rev. B 94, 014105] Published Fri Jul 08, 2016

]]>Although defect clusters are detrimental to the electronic and mechanical properties of semiconductor materials, annihilation of such clusters is limited by their lack of thermal mobility due to high migration barriers. Here, we find that small clusters in bulk SiC (a covalent material of importance…

[Phys. Rev. B 94, 024107] Published Fri Jul 08, 2016

]]>The electronic structure of hydrogen impurity in ${\mathrm{Lu}}_{2}{\mathrm{O}}_{3}$ was studied by first-principles calculations and muonium spectroscopy. The computational scheme was based on two methods which are well suited to treat defect calculations in $f$-electron systems: first, a semilocal functional of conventional dens…

[Phys. Rev. B 94, 014104] Published Thu Jul 07, 2016

]]>The control of octahedral rotations in perovskite heterostructures is an emerging strategy for inducing new functionality as evidenced by recent predictions of improper ferroelectricity, polar metals, and multiferroics. Many of these predictions are predicated on the presence of a specific rotation pattern (${a}^{-}\phantom{\rule{0}{0ex}}{a}^{-}\phantom{\rule{0}{0ex}}{c}^{+}$) in superlattices that exhibit the orthorhombic ($P\phantom{\rule{0}{0ex}}b\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}m$) perovskite structural variant. The authors use synchrotron diffraction to measure the octahedral rotation patterns in strained ferrite, manganite, and gallate perovskite films finding that compressive strain strongly favors ${a}^{+}\phantom{\rule{0}{0ex}}{a}^{-}\phantom{\rule{0}{0ex}}{c}^{-}$ rotation patterns and tensile strain weakly favors ${a}^{-}\phantom{\rule{0}{0ex}}{a}^{-}\phantom{\rule{0}{0ex}}{c}^{+}$ structures. In contrast, films grown on orthorhombic substrates exhibit the same rotation pattern orientation as the substrate, even for epitaxial conditions where strain would favor the opposite structural orientation. The results indicate that substrate imprinting is a more robust method than strain for controlling the rotation pattern in $P\phantom{\rule{0}{0ex}}b\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}m$-type perovskite films, a finding that should enable more efficient experimental pursuits of rotation-driven ferroic states in oxide heterostructures.

[Phys. Rev. B 94, 024105] Published Thu Jul 07, 2016

]]>Ferromagnetism and superconductivity are two generally incompatible states of matter. Their coexistence has been observed only under very unusual circumstances and so far only in metals. In contrast, most semiconductors are not naturally magnetic or superconducting, but introducing magnetism or superconductivity into semiconductors is seen as an important step towards radical improvement of our electronics capabilities and therefore a hotly pursued goal. Here, the authors report the discovery of superconductivity coexisting with ferromagnetism in the semiconducting material samarium nitride (SmN). The large intrinsic exchange splitting of the conduction band in SmN requires the superconducting order to be of unconventional (likely $p$-wave) type. Superconductivity is observed to be even further enhanced in superlattices where layers of SmN alternate with layers made of the strongly ferromagnetic but non-superconducting material gadolinium nitride. These features render SmN an interesting laboratory for understanding more about the fundamentals of ferromagnetism and superconductivity in semiconductors and exploring opportunities for integrating superconducting spintronics into the design of semiconductor-based electronic devices.

[Phys. Rev. B 94, 024106] Published Thu Jul 07, 2016

]]>We have determined positron annihilation characteristics (lifetime and Doppler broadening) in six basic vacancy-type defects of $6H$-SiC and two nitrogen-vacancy complexes using *ab initio* calculations. The positron characteristics obtained allow us to point out which positron technique in the most ada…

[Phys. Rev. B 94, 014103] Published Wed Jul 06, 2016

]]>The size limitation of *ab initio* calculations impedes first-principles simulations of crystal defects at nanometer sizes. Considering clusters of self-interstitial atoms as a paradigm for such crystal defects, we have developed an *ab initio*–accuracy model to predict formation energies of defect clus…

[Phys. Rev. B 94, 024103] Published Wed Jul 06, 2016

]]>Lead fluoride, $\mathrm{Pb}{\mathrm{F}}_{2}$, was investigated experimentally in the laser-heated diamond anvil cell by x-ray diffraction to pressures of 75 GPa at room temperature and to 64.5 GPa and 2430 K, as well as through first-principles density functional theory calculations up to 70 GPa. During room temperature com…

[Phys. Rev. B 94, 024104] Published Wed Jul 06, 2016

]]>We present a structural and magnetic phase diagram of the solid solution ${\text{LaCo}}_{x}{\text{Mn}}_{1-x}{\text{O}}_{3}$. We show by neutron diffraction that the monoclinic structure previously observed for the elpasolite form ${\text{La}}_{2}{\text{CoMnO}}_{6}$ (${\text{LaCo}}_{0.5}{\text{Mn}}_{0.5}{\text{O}}_{3}$) is also observed for another member of the solid solution $x\phantom{\rule{0.28em}{0ex}}=\phantom{\rule{0.28em}{0ex}}0.35$. We also present…

[Phys. Rev. B 94, 014102] Published Tue Jul 05, 2016

]]>The photophysics and charge state dynamics of the nitrogen vacancy (NV) center in diamond has been extensively investigated, but is still not fully understood. In contrast to previous work, we find that ${\mathrm{NV}}^{0}$ converts to ${\mathrm{NV}}^{-}$ under excitation with low power near-infrared (1064-nm) light, resulting in *i…*

[Phys. Rev. B 94, 024101] Published Tue Jul 05, 2016

]]>We studied the two-step martensitic transition of a Cu-Al-Ni shape-memory alloy by calorimetry, acoustic emission (AE), and resonant ultrasound spectroscopy (RUS) measurements. The transition occurs under cooling from the cubic $(\beta ,Fm3m)$ parent phase near 242 K to a mixture of orthorhombic $2H$ and mo…

[Phys. Rev. B 94, 024102] Published Tue Jul 05, 2016

]]>We compare extended x-ray absorption fine structure (EXAFS) data at the Zn K edge for a low concentration of Zn (0.7 mol%) in a stoichiometric crystal with that for higher Zn concentrations (nominally 5 and 9 mol%) in congruent ${\mathrm{LiNbO}}_{3}$ (LNO). Note that stoichiometric and congruent LNO have significan…

[Phys. Rev. B 94, 014101] Published Fri Jul 01, 2016

]]>We report a joint experimental and theoretical study of the optical properties of tetragonal bismuth oxide ($\beta -\mathrm{B}{\mathrm{i}}_{2}{\mathrm{O}}_{3}$) at high pressure by means of optical absorption measurements combined with *ab initio* electronic band structure calculations. Our results are consistent with previous results that show…

[Phys. Rev. B 93, 224111] Published Thu Jun 30, 2016

]]>A systematic *ab initio* study of the influence of local magnetism on the generalized stacking fault energy (GSFE) surface in pure *fcc* iron at 0 K has been performed. In the calculations we considered ferro- and antiferro- (single- and double-layer) magnetic order of local moments as well as their com…

[Phys. Rev. B 93, 214115] Published Wed Jun 29, 2016

]]>We combine the ideas of intensity interferometry, polarization optics, and Bell's measurement into an experimental proposal which is hosted in a $\nu =2$ quantum Hall (QH) edge state. Our interferometer comprises of a single gate, that separates the spin-resolved edge states of $\nu =2$ state. An analog of wa…

[Phys. Rev. B 93, 220101(R)] Published Wed Jun 29, 2016

]]>Pressure-dependent powder x-ray diffraction, Raman spectroscopy, and dielectric constant measurements are performed on 0.$65{\mathrm{BiFeO}}_{3}\text{\u2212}0.35{\mathrm{PbTiO}}_{3}$. Four structural transitions are reported in 0–34 GPa range. The transitions are observed at 0.7(1), 0.8(1), 3.4(1), and 6.1(1) GPa, where the system transform…

[Phys. Rev. B 93, 214114] Published Tue Jun 28, 2016

]]>In recent years, material-induced noise arising from defects has emerged as an impediment to quantum-limited measurement in systems ranging from microwave qubits to gravity-wave interferometers. As experimental systems push to ever smaller dimensions, extrinsic system properties can affect its inter…

[Phys. Rev. B 93, 224110] Published Tue Jun 28, 2016

]]>Many grain boundaries (GBs) in crystalline materials develop highly disordered, liquidlike structures at high temperatures. In alloys, this premelting effect can be fueled by solute segregation and can occur at lower temperatures than in single-component systems. A premelted GB can be modeled by a t…

[Phys. Rev. B 93, 224108] Published Mon Jun 27, 2016

]]>Pressure-induced transitions from ordered intermetallic phases to substitutional alloys to semi-ordered phases were studied in a series of bismuth tellurides. By using angle-dispersive x-ray diffraction, the compounds ${\mathrm{Bi}}_{4}{\mathrm{Te}}_{5}$, BiTe, and ${\mathrm{Bi}}_{2}\mathrm{Te}$ were observed to form alloys with the disordered body-cent…

[Phys. Rev. B 93, 224109] Published Mon Jun 27, 2016

]]>Strained ${\mathrm{NaNbO}}_{3}$ films of different thicknesses are epitaxially grown on (110) ${\mathrm{NdGaO}}_{3}$ substrates. A detailed analysis of the permittivity of these films demonstrates that strain not only leads to a modification of the permittivity and the ferroelectric transition temperature, it also results in a pro…

[Phys. Rev. B 93, 224107] Published Wed Jun 22, 2016

]]>We explore the reactivity of xenon with sulfur under high pressure, using unbiased structure searching techniques combined with first-principles calculations, which identify a stable ${\mathrm{XeS}}_{2}$ compound crystallized in a Laves phase with hypercoordinated (16-fold) Xe at 191 GPa and 0 K. Taking the thermal…

[Phys. Rev. B 93, 214112] Published Tue Jun 21, 2016

]]>We report on a drastic change of the Ni collective magnetization dynamics when incorporated into a $\mathrm{Ni}\text{/}{\mathrm{V}}_{2}{\mathrm{O}}_{3}$ heterostructure. Two, unexpected, well-defined Ni ferromagnetic resonance (FMR) modes are observed in the coexistence region of the first-order ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$ structural phase transition (SPT). The phase…

[Phys. Rev. B 93, 214113] Published Tue Jun 21, 2016

]]>The effect of composition on the antiphase boundary (APB) energy of Ni-based $\mathrm{L}{1}_{2}$-ordered alloys is investigated by *ab initio* calculations employing the coherent potential approximation. The calculated APB energies for the {111} and {001} planes reproduce experimental values of the APB energy. The AP…

[Phys. Rev. B 93, 224106] Published Mon Jun 20, 2016

]]>Understanding the spontaneous emergence of dislocation patterns during plastic deformation is a long standing challenge in dislocation theory. During the past decades several phenomenological continuum models of dislocation patterning were proposed, but few of them (if any) are derived from microsco…

[Phys. Rev. B 93, 214110] Published Fri Jun 17, 2016

]]>Because of the enormous range of time and space scales involved in dislocation dynamics, plastic modeling at macroscale requires a continuous formulation. In this paper, we present a rigorous formulation of the transition between the discrete, where plastic flow is resolved at the scale of individua…

[Phys. Rev. B 93, 214111] Published Fri Jun 17, 2016

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