We present results of a temperature-dependent high-resolution synchrotron x-ray powder diffraction study of sequence of phase transitions in $\mathrm{N}{\mathrm{i}}_{2}\mathrm{MnGa}$. Our results show that the incommensurate martensite phase results from the incommensurate premartensite phase and not from the austenite phase assumed…

[Phys. Rev. B 92, 054112] Published Fri Aug 28, 2015

]]>Ferroelectricity in strain-free and strained double perovskite fluorides, ${\mathrm{Na}}_{3}{\mathrm{ScF}}_{6}$ and ${\mathrm{K}}_{2}{\mathrm{NaScF}}_{6}$, is investigated using first-principles density functional theory. Although the experimental room temperature crystal structures of these fluoroscandates are centrosymmetric, i.e., ${\mathrm{Na}}_{3}{\mathrm{ScF}}_{6}$ ($P{2}_{1}/n$) and ${\mathrm{K}}_{2}{\mathrm{Na\dots}}_{}$

[Phys. Rev. B 92, 054111] Published Thu Aug 27, 2015

]]>The lattice structure and symmetry of two-dimensional (2D) layered materials are of key importance to their fundamental mechanical, thermal, electronic, and optical properties. Raman spectroscopy, as a convenient and nondestructive tool, however, has its limitations in identifying all symmetry allow…

[Phys. Rev. B 92, 054110] Published Wed Aug 26, 2015

]]>Polarization switching kinetics is one of the key issues for future development of nanoelectronic devices based on ferroelectrics. Up to now, such kinetics still remains poorly studied despite its crucial impact on the device performances. Here, the switching mechanism in 11-nm-thick ferroelectric f…

[Phys. Rev. B 92, 060102(R)] Published Wed Aug 26, 2015

]]>The effects of normal compressive strain and in-plane strain on the structures of phosphorene have been investigated by using first-principles calculations. It is quite intriguing to find that a structural transformation from pristine Z-phosphorene to a new A-phosphorene occurs under the normal comp…

[Phys. Rev. B 92, 064114] Published Tue Aug 25, 2015

]]>In this work we aim to resolve the counterintuitive diffusion behavior of Fe and N atoms in an iron mononitride (FeN) thin film. It was observed that in spite of their larger size, Fe atoms tend to diffuse more rapidly than smaller N atoms. This only happens in the N-rich region of the Fe-N phase di…

[Phys. Rev. B 92, 054109] Published Mon Aug 24, 2015

]]>The sound velocity of Mo along the Hugoniot adiabat is calculated from first principles using density-functional theory based molecular dynamics. These data are compared to the sound velocity as measured in recent experiments. The theoretical and experimental Hugoniot and sound velocities are in ver…

[Phys. Rev. B 92, 060101(R)] Published Mon Aug 24, 2015

]]>We present a rigorous irreversible thermodynamics treatment of creep deformation of solid materials with interfaces described as geometric surfaces capable of vacancy generation and absorption and moving under the influence of local thermodynamic forces. The free energy dissipation rate derived in t…

[Phys. Rev. B 92, 064113] Published Mon Aug 24, 2015

]]>The local structures around Co and Fe in ${\mathrm{BiCo}}_{1-x}{\mathrm{Fe}}_{x}{\mathrm{O}}_{3}$ (BCFO) have been determined element-selectively by means of extended x-ray absorption fine structure (EXAFS) measurements at the Co and Fe $K$ edges. In the tetragonal (T) phase at $x\le 0.63$, both Fe and Co ions are trivalent and locate in the ${\mathrm{O}}_{5}$ pyra…

[Phys. Rev. B 92, 054108] Published Fri Aug 21, 2015

]]>The structural transitions of the ground state of a system of repulsively interacting particles confined in a quasi-one-dimensional channel, and the effect of the interparticle interaction as well as the functional form of the confinement potential on those transitions are investigated. Although the…

[Phys. Rev. B 92, 064112] Published Fri Aug 21, 2015

]]>Structural changes of ${\mathrm{Li}}_{2}{\mathrm{C}}_{2}$ under pressure were studied by synchrotron x-ray diffraction in a diamond anvil cell under hydrostatic conditions and by using evolutionary search methodology for crystal structure prediction. We show that the high-pressure polymorph of ${\mathrm{Li}}_{2}{\mathrm{C}}_{2}$, which forms from the $Immm$ gr…

[Phys. Rev. B 92, 064111] Published Wed Aug 19, 2015

]]>Phase competition and the subsequent phase selection are important characteristics of alloy systems exhibiting numerous states of distinct symmetry but comparable energy. The stoichiometric ${\mathrm{Co}}_{2}\mathrm{NiGa}$ Heusler alloy exhibits a martensitic transformation with concomitant reduction in symmetry from an aus…

[Phys. Rev. B 92, 054107] Published Thu Aug 13, 2015

]]>The phase diagram of solid oxygen in the magnetic-field-temperature ($B-T$) plane is revealed by magnetization and magnetotransmission measurements. The high-field phase of solid oxygen, which we term the $\theta $ phase, is induced at the temperature below 42 K. The transition fields at the $\alpha -\theta $ and $\beta -\theta $ trans…

[Phys. Rev. B 92, 064109] Published Thu Aug 13, 2015

]]>We have explored the high-pressure structural, vibrational, electronic, and magnetic behavior of the multiferroic $\mathrm{CoC}{\mathrm{r}}_{2}{\mathrm{O}}_{4}$ spinel up to 30 GPa by means of x-ray diffraction, Raman spectroscopy, and density functional theory calculations. Our investigations revealed a reversible tetragonal distortion …

[Phys. Rev. B 92, 064108] Published Wed Aug 12, 2015

]]>From the energies of various noncollinearly ordered spin configurations of ${\mathrm{YMnO}}_{3}$ obtained using first-principles density functional theory and spin-orbit coupling, we demonstrate a remarkable magnetocrystalline anisotropy in the ordering of spins of ${\mathrm{Mn}}^{3+}$ ions. We find that these spins are confined i…

[Phys. Rev. B 92, 054106] Published Tue Aug 11, 2015

]]>Using *ab initio* calculations and symmetrized plane waves, we analyze the basal-plane generalized stacking fault energies in pure Mg and Mg-Y alloys and show that the knowledge of energies of only five specific points is sufficient to accurately predict the core structures and Peierls stresses of $\langle a\rangle $…

[Phys. Rev. B 92, 064107] Published Tue Aug 11, 2015

]]>The quasiharmonic (QH) approximation uses harmonic vibrational frequencies ${\omega}_{Q,H}\left(V\right)$ computed at volumes $V$ near ${V}_{0}$ where the Born-Oppenheimer (BO) energy ${E}_{\mathrm{el}}\left(V\right)$ is minimum. When this is used in the harmonic free energy, QH approximation gives a good zeroth order theory of thermal expansion and first-o…

[Phys. Rev. B 92, 064106] Published Mon Aug 10, 2015

]]>We report systematic diffuse x-ray scattering measurements of the elastic strain fields generated by oxygen vacancies in strained bulk ${\mathrm{SrTiO}}_{3}$ crystals. Diffuse x-ray scattering has been used for decades to measure the elastic strain fields generated by point defects based on the assumptions that the…

[Phys. Rev. B 92, 064105] Published Fri Aug 07, 2015

]]>The structural transformation of multiferroic ${\mathrm{EuTiO}}_{3}$ has been intensively investigated by synchrotron x-ray diffraction at pressures up to 50.3 GPa and temperatures from 50 to 500 K. A pressure-induced antiferrodistortive phase transition from cubic $Pm\overline{3}m$ to tetragonal $I4/mcm$ space group has been ob…

[Phys. Rev. B 92, 064102] Published Thu Aug 06, 2015

]]>Modeling of nanostructure evolution in solids requires comprehensive data on the properties of defects such as the vacancy and foreign atoms. Since most processes occur at elevated temperatures, not only the energetics of defects in the ground state, but also their temperature-dependent free energie…

[Phys. Rev. B 92, 064103] Published Thu Aug 06, 2015

]]>Single spin carrying defects are key elements in quantum information and nanosensing technology with the nitrogen-vacancy (NV) center in diamond being the outstanding example. In a combined electron paramagnetic resonance and first-principles modeling study we verify the existence of such NV centers…

[Phys. Rev. B 92, 064104] Published Thu Aug 06, 2015

]]>Biaxial strain in coherent epitaxial thin films can have a pronounced effect on the point-defect profile in the films' material. Detailed fundamental knowledge of the interaction of strain with point defects is crucial to understanding the stoichiometry and resulting properties of strained thin film…

[Phys. Rev. B 92, 054103] Published Wed Aug 05, 2015

]]>Using the dynamical matrix of a crystal obtained from *ab initio* calculations, we have evaluated the strength of the dynamic flexoelectric effect and found it comparable to that of the static bulk flexoelectric effect, in agreement with earlier order-of-magnitude estimates. We also propose a method o…

[Phys. Rev. B 92, 054104] Published Wed Aug 05, 2015

]]>We present here a first-principles study of the ternary compounds formed by Ni, In, and As, a material of great importance for self-aligned metallic contacts in next-generation InAs-based MOS transistors. The approach we outline is general and can be applied to study the crystal structure and proper…

[Phys. Rev. B 92, 054105] Published Wed Aug 05, 2015

]]>Ferroelectric thin films are considered to be among the top candidates for room-temperature electrocaloric materials as they exhibit excellent electric properties and allow application of record high electric fields. At the same time, downsizing of ferroelectric electrocalorics brings about an unwan…

[Phys. Rev. B 92, 064101] Published Wed Aug 05, 2015

]]>Hexagonal $\mathrm{ErFe}{\mathrm{O}}_{3}$ thin films fabricated by a pulsed laser deposition method were investigated by x-ray diffraction (XRD) and transmission electron microscopy. No structural phase transition was observed between 20 and 900 K. Ferroelectric $D-E$ hysteresis loops were obtained at room temperature using t…

[Phys. Rev. B 92, 054101] Published Mon Aug 03, 2015

]]>The pressure-induced structural phase transition in the intermediate-valence compound CeNi has been investigated by x-ray and neutron powder diffraction techniques. It is shown that the structure of the pressure-induced CeNi phase (phases) can be described in terms of the $Pnma$ space group. Equations…

[Phys. Rev. B 92, 054102] Published Mon Aug 03, 2015

]]>EuTiO${}_{3}$ has been attracting considerable attention due to its large magnetoelectric effect and its potential for future applications. In this work the authors focus on the structural phase transition that bears resemblance to the prototypical phase transition in isostructural SrTiO${}_{3}$ but takes place at much higher temperatures ${T}_{S}$. The authors perform a detailed study of poly- and single-crystalline EuTiO${}_{3}$ and EuTi${}_{1-x}$Nb${}_{x}$O${}_{3}$ using synchrotron X-ray diffraction, Resonant Ultrasound Spectroscopy, and magnetization measurements. They find an unexpectedly rapid increase of ${T}_{S}$ when EuTiO${}_{3}$ is doped with niobium. Another notable result of the Nb doping, which is confirmed in this study for single-crystalline samples, is an unusual transformation of the low-temperature phase from an antiferromagnetic to ferromagnetic state at $x=0.1$.

[Phys. Rev. B 92, 024109] Published Thu Jul 30, 2015

]]>The $\mathrm{H}{\mathrm{o}}_{2}\mathrm{T}{\mathrm{i}}_{2}{\mathrm{O}}_{7},\mathrm{E}{\mathrm{r}}_{2}\mathrm{T}{\mathrm{i}}_{2}{\mathrm{O}}_{7}$, and $\mathrm{Y}{\mathrm{b}}_{2}\mathrm{T}{\mathrm{i}}_{2}{\mathrm{O}}_{7}$ pyrochlores were studied by synchrotron x-ray diffraction to determine whether the (002) peak, forbidden in the pyrochlore space group $Fd-3m$ but observed in single crystal neutron scattering measurements, is present due to a deviation of their pyrochlore structur…

[Phys. Rev. B 92, 024110] Published Thu Jul 30, 2015

]]>The high-pressure behavior of natural henritermierite garnet with close to end-member composition ${\mathrm{Ca}}_{3}{\mathrm{Mn}}_{2}\left[{\mathrm{SiO}}_{4}{]}_{2}\right[{\mathrm{O}}_{4}{\mathrm{H}}_{4}]$ was studied at pressures up to 80 GPa using single-crystal synchrotron x-ray diffraction, Raman spectroscopy, and quantum-mechanical calculations based on density functional theory. …

[Phys. Rev. B 92, 014117] Published Wed Jul 29, 2015

]]>Utilizing single-crystal synchrotron x-ray scattering, we observe distorted ${\text{CuO}}_{2}$ planes in the electron-doped superconductor ${\mathrm{Pr}}_{1-x}{\mathrm{LaCe}}_{x}{\mathrm{CuO}}_{4+\delta},x$ = 0.12. Resolution-limited rods of scattering are indicative of a long-range two-dimensional $2\sqrt{2}\times 2\sqrt{2}$ superstructure in the $a-b$ plane, adhering to planar spac…

[Phys. Rev. B 92, 014118] Published Wed Jul 29, 2015

]]>Taking advantage of the new opportunities provided by x-ray free electron laser (FEL) sources when coupled to a long laser pulse as available at the Linear Coherent Light Source (LCLS), we have performed x-ray absorption near-edge spectroscopy (XANES) of laser shock compressed iron up to 420 GPa ($\pm \mathrm{5\dots}$

[Phys. Rev. B 92, 024108] Published Wed Jul 29, 2015

]]>The Jahn-Teller effect is a fascinating and ubiquitous phenomenon in modern quantum physics and chemistry. We propose a class of oxides with a melilite structure ${\mathrm{Ba}}_{2}T{\mathrm{Ge}}_{2}{\mathrm{O}}_{7}$ $(T=\text{V},\text{Ni})$ where Jahn-Teller distortions are mainly responsible for the appearance of electric polarization. At the heart of the p…

[Phys. Rev. B 92, 014116] Published Mon Jul 27, 2015

]]>In this Comment we discuss recent results presented by Nguyen *et al.* on shock compressed molybdenum up to 438 GPa [Phys. Rev. B **89**, 174109 (2014)]. The aim of Nguyen's article is to show that there is no phase transition near 210 GPa. We propose instead an interpretation of their data that this mate…

[Phys. Rev. B 92, 026101] Published Mon Jul 27, 2015

]]>We respond to the Comment by Errandonea *et al.* [Phys. Rev. B **92**, 026101 (2015)] on their reinterpretation of our published data [Nguyen *et al.*, Phys. Rev. B **89**, 174109 (2014)]. In the original paper, we argued that there is no solid-solid phase transition along the Hugoniot at 2.1 Mbars. There is, …

[Phys. Rev. B 92, 026102] Published Mon Jul 27, 2015

]]>In this work we performed 2.5-dimensional (2.5D) dislocation dynamics simulations coupling climb with the glide dislocation motion to model the creep behavior of olivine, one of the main component of the Earth's upper mantle. In particular, we present an application of this method to determine the c…

[Phys. Rev. B 92, 014115] Published Thu Jul 23, 2015

]]>The preparations of single (monolayer) and bulk carbides on the $\mathrm{Mo}\left(110\right)$ and $\mathrm{Mo}\left(100\right)$ single crystals are followed *in situ* at 1200 K using synchrotron-based high-resolution x-ray photoelectron spectroscopy of the $\mathrm{C}\phantom{\rule{0.28em}{0ex}}1s$ and core Mo $3{d}_{5/2}$ levels. By comparing the experimental results to first principles c…

[Phys. Rev. B 92, 014114] Published Wed Jul 22, 2015

]]>The irreversibility of the martensite transition in magnetic shape memory alloys (MSMAs) with respect to the external magnetic field is one of the biggest challenges that limits their application as giant caloric materials. This transition is a magnetostructural transition that is accompanied with a…

[Phys. Rev. B 92, 020105(R)] Published Wed Jul 22, 2015

]]>The electronic structure of thallium rhenium oxide (${\mathrm{TlReO}}_{4}$) at room temperature is explored as a function of applied pressure using a diamond-anvil cell and high-resolution x-ray absorption spectroscopy. We show possible evidence of charge transfer from the thallium to the rhenium atom in the high-p…

[Phys. Rev. B 92, 014113] Published Tue Jul 21, 2015

]]>The nucleation, growth, and propagation of like-spin domains in spin-crossover materials was investigated during the relaxation process of a metastable HS state at low temperature using an electroelastic model running on a deformable two-dimensional square lattice. We distinguish the onset of patter…

[Phys. Rev. B 92, 014111] Published Mon Jul 20, 2015

]]>The experimental observation of an efficient second-order nonlinearity with dominating frequency upconversion is reported for one-dimensional (1D) guided elastic waves localized at solid edges. These 1D acoustic wedge waves are a fundamental type of elastic wave with a phase velocity below that of s…

[Phys. Rev. B 92, 014112] Published Mon Jul 20, 2015

]]>High-performance refractory materials play an important role in applications ranging from gas turbines to heat shields for hypersonic vehicles. The authors carried out an extensive first-principles investigation into the melting temperatures of the refractory Hf-C and Hf-Ta-C systems, which hold the highest melting temperatures known to date, and identified the major factors that contribute to the high melting temperatures. A new class of materials were proposed and explored, which, according to the calculation, may increase the current melting point record by up to 200 K. This work demonstrates the feasibility and usefulness of large-scale first-principles calculations for high-throughput materials screening on a high-level thermodynamic property.

[Phys. Rev. B 92, 020104(R)] Published Mon Jul 20, 2015

]]>A range of compelling information on the local structure and dynamics of the ferroelectric perovskite-type $\left({\mathrm{ABO}}_{3}\right)$ system $(1-x){\mathrm{PbTiO}}_{3}-x{\mathrm{BiScO}}_{3}$ has been revealed through analyzing room-temperature x-ray pair distribution functions and temperature-dependent Raman scattering data for compositions ranging…

[Phys. Rev. B 92, 024107] Published Wed Jul 15, 2015

]]>Shock-induced freezing in liquids has long been a subject of interest as well as mystery. With large-scale molecular dynamics simulations, we demonstrate that homogeneous crystal nucleation in liquid Cu can be realized under effective supercooling $\left(\theta \right)$, via quasi-isentropic compression or ramp wave l…

[Phys. Rev. B 92, 014108] Published Mon Jul 13, 2015

]]>Complex metallic alloys having isolated transition-metal elements in the surface layer have been reported to work well as selective hydrogenation catalysts. We report an experimental determination of the surface structure of one such compound $\mathrm{A}{\mathrm{l}}_{13}\mathrm{F}{\mathrm{e}}_{4}\left(010\right)$. The structure was determined using low-ener…

[Phys. Rev. B 92, 014109] Published Mon Jul 13, 2015

]]>We present a comprehensive set of first-principles electronic structure calculations of the properties of substitutional transition metal solutes and point defects in austenite (face-centered cubic, paramagnetic Fe). Clear trends were observed in these quantities across the transition metal series, …

[Phys. Rev. B 92, 014110] Published Mon Jul 13, 2015

]]>Phase transformations in metallic grain boundaries (GBs) present significant fundamental interest in the context of thermodynamics of low-dimensional physical systems. We report on atomistic computer simulations of the Cu-Ag system that provide direct evidence that GB phase transformations in a sing…

[Phys. Rev. B 92, 020103(R)] Published Mon Jul 13, 2015

]]>The composition-dependent crystal structure, elastic modulus, phase stability, and magnetic property of ${\mathrm{Ni}}_{2-x}{\mathrm{Co}}_{x}{\mathrm{Mn}}_{1.60}{\mathrm{Sn}}_{0.40}\phantom{\rule{4.pt}{0ex}}\left(0\le x\le 0.50\right)$ are studied by using first-principles calculations in combination with atomistic spin dynamics method. It is shown that the present lattice parameters and Curie temp…

[Phys. Rev. B 92, 024105] Published Mon Jul 13, 2015

]]>We present an automated scheme to systematically sample energy landscapes of crystalline solids, based on the ideas of metadynamics and evolutionary algorithms. Phase transitions are driven by the evolution of the order parameter (in this case, 6-dimensional order parameters composed of cell vectors…

[Phys. Rev. B 92, 024106] Published Mon Jul 13, 2015

]]>We used density functional theory (DFT) calculations to model the interaction of hydrogen atoms and molecules with strained bonds and neutral oxygen vacancies in amorphous silica $\left({\text{a-SiO}}_{2}\right)$. The results demonstrate that the interaction of atomic hydrogen with strained Si–O bonds in defect-free ${\text{a-SiO}}_{2}$ …

[Phys. Rev. B 92, 014107] Published Fri Jul 10, 2015

]]>The physical state and properties of silicates at conditions encountered in the cores of gas giants, ice giants, and of Earth-like exoplanets now discovered with masses up to several times the mass of the Earth remain mostly unknown. Here, we report on theoretical predictions of the properties of si…

[Phys. Rev. B 92, 014105] Published Wed Jul 08, 2015

]]>Data-driven approaches are particularly useful for computational materials discovery and design as they can be used for rapidly screening over a very large number of materials, thus suggesting lead candidates for further in-depth investigations. A central challenge of such approaches is to develop a…

[Phys. Rev. B 92, 014106] Published Wed Jul 08, 2015

]]>We propose a local real-space formulation for orbital-free density functional theory (DFT) with density dependent kinetic energy functionals and a unified variational framework for computing the configurational forces associated with geometry optimization of both internal atomic positions as well as…

[Phys. Rev. B 92, 014104] Published Tue Jul 07, 2015

]]>The morphology transition from the thermodynamically favorable to the unfavorable phase during growth of freestanding copper nanoclusters is studied by molecular dynamics simulations. We give a detailed description of the kinetics and thermodynamics of the process. A universal mechanism of a solid-s…

[Phys. Rev. B 92, 020102(R)] Published Tue Jul 07, 2015

]]>The thermal evolution of electronic order in the complex Verwey ground state of magnetite $\left(\mathrm{F}{\mathrm{e}}_{3}{\mathrm{O}}_{4}\right)$ has been determined through 22 high-accuracy synchrotron x-ray structure refinements using three $10\u201340\phantom{\rule{0.16em}{0ex}}\mu \mathrm{m}$ grains of stoichiometric magnetite. A robust fitting function is introduced to extract values of …

[Phys. Rev. B 92, 024104] Published Tue Jul 07, 2015

]]>Precise characterization of a system's Hamiltonian is crucial to its high-fidelity control that would enable many quantum technologies, ranging from quantum computation to communication and sensing. In particular, nonsecular parts of the Hamiltonian are usually more difficult to characterize, even i…

[Phys. Rev. B 92, 020101(R)] Published Mon Jul 06, 2015

]]>X-ray absorption near-edge spectroscopy, photoluminescence, cathodoluminescence, and Raman spectroscopy have been used to investigate the chemical states of nitrogen dopants in ZnO nanowires. It is found that nitrogen exists in multiple states: ${\mathrm{N}}_{\mathrm{O}},\phantom{\rule{0.16em}{0ex}}{\mathrm{N}}_{\mathrm{Zn}}$, and loosely bound ${\mathrm{N}}_{2}$ molecule. The results esta…

[Phys. Rev. B 92, 024103] Published Mon Jul 06, 2015

]]>Density functional theory and group-theoretical methods are used to explore the origin for ferroelectricity in cation ordered ${\mathrm{LaSrMnO}}_{4}$ with the Ruddlesden-Popper structure. The equilibrium phase exhibits the polar $Pca{2}_{1}$ space group where small polar displacements of ${d}^{4}\phantom{\rule{0.28em}{0ex}}{\mathrm{Mn}}^{3+}$ coexist with antiferrodist…

[Phys. Rev. B 92, 014102] Published Thu Jul 02, 2015

]]>The elastic moduli, elastic anisotropy coefficients, sound velocities and Poisson's ratio of hcp solid helium have been calculated using density functional theory in generalized gradient approximation (up to 30 TPa), and pair + triple semiempirical potentials (up to 100 GPa). Zero-point vibrations h…

[Phys. Rev. B 92, 024102] Published Thu Jul 02, 2015

]]>Silicon materials play a key role in many technologically relevant fields, ranging from the electronic to the photovoltaic industry. A systematic search for silicon allotropes was performed by employing a modified *ab initio* minima hopping crystal structure prediction method. The algorithm was optimi…

[Phys. Rev. B 92, 014101] Published Wed Jul 01, 2015

]]>We investigated the crystal structure and lattice excitations of the ternary intermetallic stannide ${\mathrm{Ca}}_{3}{\mathrm{Ir}}_{4}{\mathrm{Sn}}_{13}$ using neutron and x-ray scattering techniques. For $T>{T}^{*}\approx 38$ K, the x-ray diffraction data can be satisfactorily refined using the space group $Pm\overline{3}n$. Below ${T}^{*}$, the crystal structure is mod…

[Phys. Rev. B 92, 024101] Published Wed Jul 01, 2015

]]>An atomistic numerical scheme is developed and used to study the prototype of relaxor ferroelectrics, that is ${\mathrm{PbMg}}_{1/3}{\mathrm{Nb}}_{2/3}{\mathrm{O}}_{3}$ (PMN), at finite temperatures. This scheme not only reproduces known complex macroscopic properties of PMN, but also provides a deep microscopic insight into this puzzling sys…

[Phys. Rev. B 91, 214117] Published Tue Jun 30, 2015

]]>The highly complex structure-property interrelationship in the lead-free piezoelectric $\left(x\right)\phantom{\rule{0.16em}{0ex}}\mathrm{N}{\mathrm{a}}_{1/2}\mathrm{B}{\mathrm{i}}_{1/2}\mathrm{Ti}{\mathrm{O}}_{3}\phantom{\rule{4.pt}{0ex}}\text{\u2212}\phantom{\rule{4.pt}{0ex}}(1-x)\phantom{\rule{0.28em}{0ex}}\mathrm{BaTi}{\mathrm{O}}_{3}$ is a subject of considerable contemporary debate. Using comprehensive x-ray, neutron diffraction, dielectric, and ferroelectric studies, we have shown the existence of a new criticali…

[Phys. Rev. B 91, 214116] Published Mon Jun 29, 2015

]]>Dislocations are central to the understanding of plasticity in metals. Using density functional theory the authors show that interstitial carbon atoms in ferritic steels stabilize a dislocation core configuration called a hard core which is otherwise unstable. Since, as they also show, at equilibrium all dislocations are expected to be fully decorated by carbon atoms, this has important implications for the understanding of plasticity in ferritic steels. It is expected that the picture developed here could also be applicable to other solutes besides carbon and to other metals besides iron.

[Phys. Rev. B 91, 220102(R)] Published Mon Jun 29, 2015

]]>We experimentally demonstrate a three-dimensional x-ray ptychography in combination with precession measurements that can reconstruct multisection images of optically thick objects. We collect a tilt-series ptychographic diffraction data set of a four-layered object and then successfully reconstruct…

[Phys. Rev. B 91, 214114] Published Thu Jun 25, 2015

]]>Using an optical interferometric method, the cavitation density of bulk superfluid helium at $T=0.96\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ is measured and found to be ${\rho}_{\mathrm{cav}}=0.1338\pm 0.0002\phantom{\rule{0.28em}{0ex}}\mathrm{g}\phantom{\rule{0.28em}{0ex}}{\mathrm{cm}}^{-3}$. A well-established equation of state for liquid helium at negative pressures converts this to the cavitation pressure ${P}_{\mathrm{cav}}=-5.1\pm 0.1\phantom{\rule{0.28em}{0ex}}\mathrm{bars}$. This cavi…

[Phys. Rev. B 91, 214115] Published Thu Jun 25, 2015

]]>A recently discovered phase of orthorhombic iron carbide o-${\mathrm{Fe}}_{7}{\mathrm{C}}_{3}$ [Prescher *et al.*, Nat. Geosci. **8**, 220 (2015)] is assessed as a potentially important phase for interpretation of the properties of the Earth's core. In this paper, we carry out first-principles calculations on o-${\mathrm{Fe}}_{7}{\mathrm{C}}_{3}$, finding properti…

[Phys. Rev. B 91, 214112] Published Wed Jun 24, 2015

]]>We present a theoretical study of the electron transmission through the AB-BA stacking boundary in multilayer graphenes. Using the tight-binding model and the transfer matrix method, we calculate the electron transmission probability through the boundary as a function of electron Fermi energy in mul…

[Phys. Rev. B 91, 214113] Published Wed Jun 24, 2015

]]>We develop statistical mechanical methods to predict the thermodynamic properties of dilute vacancies in multicomponent solids from first principles. The approach relies on a coarse-graining procedure to predict dilute vacancy concentrations with Monte Carlo simulations in alloys exhibiting varying …

[Phys. Rev. B 91, 224109] Published Wed Jun 24, 2015

]]>Branded for its potential electronic ferroelectricity, charge-ordered $\mathrm{LuF}{\mathrm{e}}_{2}{\mathrm{O}}_{4}$ has a layered Fe triangular framework, whose topology is a source of degeneracy, both at the charge and spin levels. Here we present an in-depth characterization of $\mathrm{LuF}{\mathrm{e}}_{2}{\mathrm{O}}_{4}\text{\u2212}hp$, the high-pressure $\left(hp\right)$ polymorph of $\mathrm{LuF}{\mathrm{e}}_{2}{\mathrm{O}}_{4}$, …

[Phys. Rev. B 91, 214111] Published Tue Jun 23, 2015

]]>Polar zinc titanate (ZnTiO${}_{3}$) is a promising lead-free ferroelectric compound with high spontaneous polarization of 75 $\mu \phantom{\rule{0}{0ex}}C/c\phantom{\rule{0}{0ex}}{m}^{2}$, which is comparable with that of PbTiO${}_{3}$. In this work a collaboration of researchers from Germany, UK, and USA present a detailed investigation of vibrational properties of ZnTiO${}_{3}$ via the high-pressure Raman spectroscopy, second-harmonic generation, and $a\phantom{\rule{0}{0ex}}b$ $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o$ calculations.

[Phys. Rev. B 91, 214110] Published Mon Jun 22, 2015

]]>Entropy barriers and aging states appear in martensitic structural-transition models, slowly re-equilibrating after temperature quenches, under Monte Carlo dynamics. Concepts from protein folding and aging harmonic oscillators turn out to be useful in understanding these nonequilibrium evolutions. W…

[Phys. Rev. B 91, 214108] Published Fri Jun 19, 2015

]]>Polarization reversal in ferroelectrics by the tip of a scanning probe microscope (SPM) has been intensively studied over the last two decades. In addition to classical domain formation and growth, a number of abnormal switching phenomena have been reported. In particular, it was experimentally and …

[Phys. Rev. B 91, 214109] Published Fri Jun 19, 2015

]]>Thermodynamic equilibrium in multicomponent solids subject to mechanical stresses is a complex nonlinear problem whose exact solution requires extensive computations. A few decades ago, Larché and Cahn proposed a linearized solution of the mechanochemical equilibrium problem by introducing the conce…

[Phys. Rev. B 91, 224107] Published Fri Jun 19, 2015

]]>Solid ${\mathrm{CS}}_{2}$ is superficially similar to ${\mathrm{CO}}_{2}$, with the same $Cmca$ molecular crystal structure at low pressures, which has suggested similar phases also at high pressures. We carried out an extensive first-principles evolutionary search in order to identify the zero-temperature lowest-enthalpy structures…

[Phys. Rev. B 91, 224108] Published Fri Jun 19, 2015

]]>We study point-defect diffusion in crystalline silicon using the kinetic activation-relaxation technique (k-ART), an off-lattice kinetic Monte Carlo method with on-the-fly catalog building capabilities based on the activation-relaxation technique (ART nouveau), coupled to the standard Stillinger-Web…

[Phys. Rev. B 91, 224106] Published Tue Jun 16, 2015

]]>The dynamical competition between the chemical mixing forced during energetic particle irradiation and thermally activated decomposition can lead to the stabilization of self-organized steady states in alloy systems comprised of immiscible elements. Continuum modeling and atomistic simulations predi…

[Phys. Rev. B 91, 214107] Published Mon Jun 15, 2015

]]>We study the entanglement spectrum of a translationally invariant lattice system under a random partition, implemented by choosing each site to be in one subsystem with probability $p\in [0,1]$. We apply this random partitioning to a translationally invariant (i.e., clean) topological state, and argue on…

[Phys. Rev. B 91, 220101(R)] Published Mon Jun 15, 2015

]]>Aluminum has been used prolifically as an impedance matching standard in the multimegabar regime (1 Mbar = 100 GPa), particularly in nuclear driven, early laser driven, and early magnetically driven flyer plate experiments. The accuracy of these impedance matching measurements depends upon the knowl…

[Phys. Rev. B 91, 224105] Published Mon Jun 15, 2015

]]>Static strain aging, a phenomenon caused by diffusion of solute atoms to dislocations, is an important contributor to the strength of substitutional alloys. Accurate modeling of this complex process requires both atomic spatial resolution and diffusional time scales, which is very challenging to ach…

[Phys. Rev. B 91, 224103] Published Fri Jun 12, 2015

]]>The exact mechanism responsible for the ferroelectricity in hexagonal manganite has been the subject of intense debate. Whether ferroelectricity and ferroelastic order appear at the same temperature and the role of covalency in the ferroelectric order are still discussed. High-temperature phase tran…

[Phys. Rev. B 91, 224104] Published Fri Jun 12, 2015

]]>Recent shock compression experiments produced clear evidence of a new carbon phase, but a full structural identification has remained elusive. Here we establish by *ab initio* calculations a body-centered cubic carbon phase in $Ia\overline{3}d\phantom{\rule{0.28em}{0ex}}\left({O}_{h}^{10}\right)$ symmetry, which contains twelve atoms in its primitive cell, th…

[Phys. Rev. B 91, 214106] Published Thu Jun 11, 2015

]]>We performed nuclear forward and inelastic scattering of synchrotron radiation by elemental Os utilizing the nuclear excited state of ${}^{187}\mathrm{Os}$ which is otherwise inaccessible using any practical radioactive decay process. The lifetime of the excited state, $3.06\left(8\right)\phantom{\rule{4.pt}{0ex}}\text{ns}$, and the energy of the transition, $\mathrm{9\dots}$

[Phys. Rev. B 91, 224102] Published Thu Jun 11, 2015

]]>Mn is used as a dopant to improve the electromechanical properties of perovskite oxides. We investigate the effects of Mn defects and associated vacancies on the electronic and atomic properties of ${\mathrm{BaTiO}}_{3}$. Using density functional theory (DFT) and $\mathrm{DFT}+U$ we investigate the equilibrium geometry and el…

[Phys. Rev. B 91, 214105] Published Tue Jun 09, 2015

]]>Searches for low-energy tetrahedral polymorphs of carbon and silicon have been performed using density functional theory computations and the *ab initio* random structure searching approach. Several of the hypothetical phases obtained in our searches have enthalpies that are lower or comparable to tho…

[Phys. Rev. B 91, 214104] Published Mon Jun 08, 2015

]]>We present an extended x-ray absorption fine structure study of the pyrochlore Y2Ru2O7 (8–298 K). We find evidence, on a local scale, of a significant magnetoelastic coupling at the Néel temperature TN∼77K pointed out by a huge Debye-Waller σ2 factor deviation from a correlated temperature dependent…

[Phys. Rev. B 91, 224101] Published Mon Jun 08, 2015

]]>At elevated temperatures, glasses crystallize via thermally activated diffusion. However, metallic glasses can also undergo deformation-induced crystallization at very low temperatures. Here we demonstrate the crystallization of $\mathrm{A}{\mathrm{l}}_{50}\mathrm{F}{\mathrm{e}}_{50}$ metallic glasses under cyclic deformation at 50 K using molecu…

[Phys. Rev. B 91, 214103] Published Fri Jun 05, 2015

]]>In this proof-of-concept analytical study (supported by numerical examples) the authors are able to achieve controllable enhancement of the electrostriction in a metamaterial medium consisting of an array of spheres in a host medium. Accounting for material dispersion and losses for a few test cases, they show a sizable enhancement (or suppression) and tunability of the electrostrictive properties. We anticipate that this study will open interesting directions previously unexplored in metamaterials research.

[Phys. Rev. B 91, 214102] Published Thu Jun 04, 2015

]]>(100)-epitaxial ${\mathrm{SrTiO}}_{3}$ thin films having biaxial compressive strains up to $-1.60\%$ were grown on lattice mismatched substrates. Two phase transitions induced by the coupled instabilities (antiferrodistortive and ferroelectric) in ${\mathrm{SrTiO}}_{3}$ were revealed in a common set of samples investigated at tempera…

[Phys. Rev. B 91, 214101] Published Wed Jun 03, 2015

]]>${\mathrm{BiMnO}}_{3}$ is the only transition-metal perovskite oxide that is insulating and shows strong ferromagnetism in bulk. This distinctive behavior would make it a promising candidate as a magnetoelectric multiferroic if it was also a polar material, but experiments have shown that bulk ${\mathrm{BiMnO}}_{3}$ has either a v…

[Phys. Rev. B 91, 184113] Published Thu May 28, 2015

]]>Structural stabilities of the Wadsley-type bronzes $\beta \text{\u2212}{\mathrm{Ag}}_{0.33}{\mathrm{V}}_{2}{\mathrm{O}}_{5}$ and $\beta \text{\u2212}{\mathrm{Li}}_{0.33}{\mathrm{V}}_{2}{\mathrm{O}}_{5}$ (both C2/m, *Z* = 6) have been studied with single-crystal x-ray diffraction in diamond anvil cells at room temperature to 8 and 13 GPa, respectively. $\beta \text{\u2212}{\mathrm{Ag}}_{0.33}{\mathrm{V}}_{2}{\mathrm{O}}_{5}$ is stable at least to 8 GPa. $\beta \text{\u2212}{\mathrm{Li}}_{0.33}{\mathrm{V}}_{2}{\mathrm{O}}_{5}$ undergoes two p…

[Phys. Rev. B 91, 174113] Published Wed May 27, 2015

]]>${\mathrm{Sb}}_{2}{\mathrm{O}}_{3}$-based materials are of broad interest in materials science and industry. High-pressure study using diamond anvil cells shows promise in obtaining new crystal and electronic structures different from their pristine states. Here, we conducted *in situ* angle dispersive synchrotron x-ray-diffractio…

[Phys. Rev. B 91, 184112] Published Wed May 27, 2015

]]>We study experimentally the intermittent progress of the mechanically induced martensitic transformation in a Cu-Al-Be single crystal through a full-field measurement technique: the grid method. We utilize an in-house, specially designed gravity-based device, wherein a system controlled by water pum…

[Phys. Rev. B 91, 174111] Published Tue May 26, 2015

]]>By using first principles in combination with atomistic spin dynamics calculational methods, we determine the temperature-dependent free energies of the $L{2}_{1}$- and $L{1}_{0}-{\mathrm{Ni}}_{2}\left({\mathrm{Mn}}_{1-x}{\mathrm{Fe}}_{x}\right)\text{Ga}\phantom{\rule{0.28em}{0ex}}\left(0\le x\le 1\right)$, including phonon vibrational and magnetic energies. The $x$-dependent martensitic phase transformation (MPT) tem…

[Phys. Rev. B 91, 174112] Published Tue May 26, 2015

]]>Using density functional theory calculations, many researchers have predicted that various tungsten nitride compounds ${\text{N}}_{1-x}{\text{W}}_{x}\left(x\frac{1}{2}\right)$ will be “ultraincompressible” or “superhard,” i.e., as hard as or harder than diamond. Necessary conditions for such compounds are that they have large bulk and shea…

[Phys. Rev. B 91, 184110] Published Tue May 26, 2015

]]>We propose a gravitational response theory for point defects (hedgehogs) binding Majorana zero modes in (3 + 1)-dimensional superconductors. Starting in 4 + 1 dimensions, where the point defect is extended into a line, a coupling of the bulk defect texture with the gravitational field is introduced.…

[Phys. Rev. B 91, 184111] Published Tue May 26, 2015

]]>Thermodynamic Ginzburg-Landau potential for temperature- and stress-induced phase transformations (PTs) between $n$ phases is developed. It describes each of the PTs with a single order parameter without an explicit constraint equation, which allows one to use an analytical solution to calibrate each …

[Phys. Rev. B 91, 174109] Published Thu May 21, 2015

]]>We studied solid solution effects on the mechanical properties of nanocrystalline (NC) ${\mathrm{Pd}}_{100-\mathrm{x}}{\mathrm{Au}}_{\mathrm{x}}$ alloys $(0\le x<50\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.16em}{0ex}}\mathrm{at}.\%)$ at the low end of the nanoscale. Concentration has been used as control parameter to tune material properties (elastic moduli, Burgers vector, stacking fault energies) at basicall…

[Phys. Rev. B 91, 174110] Published Thu May 21, 2015

]]>We present a scaling theory for the entanglement spectrum under an external driving. Based on the static scaling of the Schmidt gap and the theory of finite-time scaling, we show that the Schmidt gap can signal the critical point and be used to estimate the critical exponents no matter in the finite…

[Phys. Rev. B 91, 184109] Published Thu May 21, 2015

]]>Vacancy properties in concentrated alloys continue to be of great interest because nowadays *ab initio* supercell simulations reach a scale where even defect properties in disordered alloys appear to be within reach. We show that vacancy properties cannot generally be extracted from supercell total en…

[Phys. Rev. B 91, 174107] Published Wed May 20, 2015

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