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

]]>We present first-principles calculations of the vibrational properties of the transition-metal dichalcogenide $1T\text{\u2212}{\mathrm{TaS}}_{2}$ for various thicknesses in the high-temperature (undistorted) phase and the low-temperature commensurate charge density wave (CDW) phase. We also present measurements of the Raman sp…

[Phys. Rev. B 93, 214109] Published Thu Jun 16, 2016

]]>The phase diagram of the Be-H system is measured up to 100 GPa. ${\mathrm{BeH}}_{2}$ is the only stoichiometry observed. Three crystalline phases are identified using synchrotron x-ray diffraction. The $Ibam$ structure, already known at ambient pressure, is stable up to 27 GPa. The $P{4}_{1}{2}_{1}2$ structure, isotypical to the…

[Phys. Rev. B 93, 224104] Published Wed Jun 15, 2016

]]>Glassy freezing dynamics was investigated in ${\mathrm{BaZr}}_{0.5}{\mathrm{Ti}}_{0.5}{\mathrm{O}}_{3}$ (BZT50) ceramic samples by means of dielectric spectroscopy in the frequency range 0.001 Hz–1 MHz at temperatures $10<T<300$ K. From measurements of the quasistatic dielectric polarization in bias electric fields up to $\sim 28$ kV/cm it has …

[Phys. Rev. B 93, 224105] Published Wed Jun 15, 2016

]]>We derived and thoroughly tested a bond-order potential (BOP) for body-centered-cubic (bcc) magnetic iron that can be employed in atomistic calculations of a broad variety of crystal defects that control structural, mechanical, and thermodynamic properties of this technologically important metal. Th…

[Phys. Rev. B 93, 214107] Published Tue Jun 14, 2016

]]>In this article, we investigate the kinetics of the iron $\alpha -\varepsilon $ transition under laser-driven ramp compression for deformation rates ranging from 3 to $9\times {10}^{7}\phantom{\rule{0.28em}{0ex}}{\mathrm{s}}^{-1}$. As in previous work, we observe a plateau in the rear surface velocity profile at the transition. With increasing deformation rate the transit…

[Phys. Rev. B 93, 214108] Published Tue Jun 14, 2016

]]>The low-temperature softening of the TO1 phonon of ${\mathrm{SrTiO}}_{3}$ (STO), which determines its incipient ferroelectricity, is known to be partially hindered either in the bulk under strong electric fields, or in thin STO films. Here we show, by terahertz (THz) reflectivity measurements, that a similar effect…

[Phys. Rev. B 93, 224103] Published Tue Jun 14, 2016

]]>By means of first-principles calculations for the SbSI semiconductor, we show that bare density functional theory fails to reproduce the experimentally observed ferroelectric phase, whereas a more advanced approach, based on hybrid functionals, correctly works. When comparing the paraelectric and fe…

[Phys. Rev. B 93, 214106] Published Fri Jun 10, 2016

]]>Motivated by recent developments in nitrogen-rich transition-metal nitrides, the stability of chromium mononitride (CrN) and the possible formation of chromium dinitride $\left(\mathrm{Cr}{\mathrm{N}}_{2}\right)$ are studied using density functional theory (with the Perdew-Burke-Ernzerhof functional within the generalized gradient app…

[Phys. Rev. B 93, 214104] Published Wed Jun 08, 2016

]]>We investigate nonlinear elastic deformations in the phase field crystal model and derived amplitude equation formulations. Two sources of nonlinearity are found, one of them is based on geometric nonlinearity expressed through a finite strain tensor. This strain tensor is based on the inverse right…

[Phys. Rev. B 93, 214105] Published Wed Jun 08, 2016

]]>In-plane heterostructures of two-dimensional (2D) materials form interface misfit dislocations to relieve lattice mismatch strain, much like heterostructures of 3D materials. Here, using graphene-hexagonal boron nitride (h-BN) as a model system, we consider interface misfit dislocations in 2D latera…

[Phys. Rev. B 93, 214103] Published Mon Jun 06, 2016

]]>Metal atom wires represent an important class of nanomaterials in the development of future electronic devices and other functional applications. Using first-principles calculations within density functional theory, we carry out a systematic study of the quantum stability of freestanding atom wires …

[Phys. Rev. B 93, 224102] Published Mon Jun 06, 2016

]]>We extend the self-consistent mean field (SCMF) method to the calculation of the Onsager matrix of Fe-based interstitial solid solutions. Both interstitial jumps and substitutional atom-vacancy exchanges are accounted for. A general procedure is introduced to split the Onsager matrix of a dilute sol…

[Phys. Rev. B 93, 224101] Published Fri Jun 03, 2016

]]>Scandium fluoride (${\mathrm{ScF}}_{3}$), having cubic ${\mathrm{ReO}}_{3}$-type structure, has attracted much scientific attention due to its rather strong negative thermal expansion (NTE) in the broad temperature range from 10 to 1100 K. Here we use the results of diffraction and extended x-ray absorption fine-structure (EXAFS) …

[Phys. Rev. B 93, 214101] Published Thu Jun 02, 2016

]]>Motivated by understanding the emergence of thermodynamic restoring forces and oscillations, we develop a quantum-mechanical model of a bath of spins coupled to the elasticity of a material. We show our model reproduces the behavior of a variety of entropic springs while enabling investigation of no…

[Phys. Rev. B 93, 214102] Published Thu Jun 02, 2016

]]>We study the structural evolution of ${\mathrm{Sr}}_{3}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$ as a function of pressure using x-ray diffraction. At a pressure of 54 GPa at room temperature, we observe a first-order structural phase transition, associated with a change from tetragonal to monoclinic symmetry and accompanied by a 4% volume collapse.…

[Phys. Rev. B 93, 174118] Published Tue May 31, 2016

]]>$\mathrm{LaOBi}{\mathrm{S}}_{2}$-type materials have drawn much attention recently because of various interesting physical properties, such as low-temperature superconductivity, hidden spin polarization, and electrically tunable Dirac cones. However, it was generally assumed that each $\mathrm{LaOBi}{\mathrm{S}}_{2}$-type compound has a unique and …

[Phys. Rev. B 93, 174119] Published Tue May 31, 2016

]]>Ferroelectrics form domain patterns that minimize their energy subject to imposed boundary conditions. In a linear, constrained theory, that neglects domain-wall energy, periodic domain patterns in the form of multirank laminates can be identified as minimum-energy states. However, when these lamina…

[Phys. Rev. B 93, 174120] Published Tue May 31, 2016

]]>We present a structural analysis of the substituted system $({\mathrm{Ba}}_{1-x}{\mathrm{Sr}}_{x}){\mathrm{CuSi}}_{2}{\mathrm{O}}_{6}$, which reveals a stable tetragonal crystal structure down to 1.5 K. We explore the structural details with low-temperature neutron and synchrotron powder diffraction, room-temperature, and cryogenic high-resolution NMR, as …

[Phys. Rev. B 93, 174121] Published Tue May 31, 2016

]]>Samarium orthoferrite $\left(\mathrm{SmFe}{\mathrm{O}}_{3}\right)$ has been the subject of debate on the existence or nonexistence of ferroelectric properties. It has a high spin-reorientation transition temperature ${T}_{\mathrm{SR}}$ (480 K). Detailed synchrotron x-ray diffraction and Raman spectroscopy dielectric investigations in the 300 to 600 K…

[Phys. Rev. B 93, 174117] Published Thu May 26, 2016

]]>We probe here the optical relaxation properties of Mg-doped wide-band-gap ${\mathrm{LiNbO}}_{3}$ single crystals with both a high spectral and temporal resolution at cryogenic temperatures. Surprisingly, we observe the photoluminescence to decay in a two-step process: a fast relaxation and a slower one centered aro…

[Phys. Rev. B 93, 174116] Published Wed May 25, 2016

]]>We report the structural changes of three $\mathrm{YF}{\mathrm{e}}_{2}{\mathrm{O}}_{4-\delta}$ ($\delta <0.1$) specimens using high resolution synchrotron x-ray powder diffraction between 80 and 300 K. All samples adopt a rhombohedral cell at room temperature (space group $R\overline{3}m$). This cell becomes unstable for the three samples on cooling, and the …

[Phys. Rev. B 93, 184110] Published Wed May 25, 2016

]]>Electric fields are known to favor long-range polar order through the aligning of electric dipoles in relation to Coulomb's force. Therefore, it would be surprising to observe a disordered polar state induced from an ordered state by electric fields. Here we show such an unusual phenomenon in a poly…

[Phys. Rev. B 93, 174114] Published Tue May 24, 2016

]]>Local distortions of the ideal periodic structure in crystals around impurity atoms play an important role in various physical properties of materials. The aim of this study was to investigate the static distortions around cadmium impurity atoms in a ${\text{SnCd}}_{0.0026}$ single crystal using atomic resolution…

[Phys. Rev. B 93, 174115] Published Tue May 24, 2016

]]>A metallic state enabled by the metal-insulator transition (MIT) in single crystal $\mathrm{V}{\mathrm{O}}_{2}\left(\mathrm{A}\right)$ nanorods is demonstrated, which provides important physical foundation in experimental understanding of MIT in $\mathrm{V}{\mathrm{O}}_{2}$. The observed tetragonal metallic state at ∼28 GPa should be interpreted as a distinct metastab…

[Phys. Rev. B 93, 184109] Published Tue May 24, 2016

]]>Accurate theoretical calculations of the nonlinear elastic response of strong solids (e.g., diamond) constitute a fundamental and important scientific need for understanding the response of such materials and for exploring the potential synthesis and design of novel solids. However, without correspo…

[Phys. Rev. B 93, 174113] Published Mon May 23, 2016

]]>Variation of the phase of the beam transmitted through a crystalline material as a function of the rocking angle is a well-known dynamical effect in x-ray scattering. Unfortunately, it is not so easy to directly measure these phase variations in a conventional scattering experiment. It was recently …

[Phys. Rev. B 93, 184107] Published Mon May 23, 2016

]]>A correct description of hydrogen diffusion and trapping is the prerequisite for an understanding of the phenomenon of hydrogen embrittlement. In this study, we carried out extensive first-principles calculations based on density functional theory to investigate the interaction of H with TiC precipi…

[Phys. Rev. B 93, 184108] Published Mon May 23, 2016

]]>The metal-insulator switching characteristics of ${\mathrm{VO}}_{2}$ play a crucial role in the performances of ${\mathrm{VO}}_{2}$-based devices. In this paper we study high-quality (010)-oriented epitaxial films grown on (001) sapphire substrates by means of electron-beam evaporation and investigate the role of interface defects…

[Phys. Rev. B 93, 184106] Published Fri May 20, 2016

]]>The traditional derivation of the elastic anomalies associated with ferroelectric (FE) phase transitions in the framework of the Landau theory is combined with the piezoelectric constitutive relations instead of being explicitly carried out with a definite expression of the FE part of the free energ…

[Phys. Rev. B 93, 174111] Published Thu May 19, 2016

]]>The structural and mechanical properties of N-doped graphene (NG) are investigated using reactive force field (ReaxFF) potentials in large-scale molecular dynamics simulations. We found that ripples, which are induced by the dopants, change the roughness of NG, which depends on the number of dopants…

[Phys. Rev. B 93, 174112] Published Thu May 19, 2016

]]>Bragg coherent x-ray diffractive imaging is a powerful technique for investigating dynamic nanoscale processes in nanoparticles immersed in reactive, realistic environments. Its temporal resolution is limited, however, by the oversampling requirements of three-dimensional phase retrieval. Here, we s…

[Phys. Rev. B 93, 184105] Published Thu May 19, 2016

]]>The mechanical properties and electronic structure of polymorphic tungsten carbides with different stacking sequences have been investigated by means of density functional theory. The stacking sequence strongly influences the stability and mechanical strength of these polymorphs. Using the plastic p…

[Phys. Rev. B 93, 184104] Published Wed May 18, 2016

]]>We report a density-functional study on the evolution of the electronic and lattice structure in ${\mathrm{BiFeO}}_{3}$ with injected electrons and holes. First, the self-trapping of electrons and holes was investigated. We found that the injected electrons tend to be localized on Fe sites due to the local lattice …

[Phys. Rev. B 93, 174110] Published Tue May 17, 2016

]]>The atomic and electronic structures of ${60}^{\circ}$ glide perfect and ${30}^{\circ}/{90}^{\circ}$ glide partial dislocations in CdTe are studied using combined semi-empirical and density functional theory calculations. The calculations predict that the dislocation cores tend to undergo significant reconstructions along the dis…

[Phys. Rev. B 93, 174109] Published Mon May 16, 2016

]]>The role of oxygen doping in CdTe is addressed by first-principles calculations. Formation energies, charge transition levels, and quasiparticle defect states are calculated within the $\text{DFT}+GW$ formalism. The formation of a new defect is identified, the $\left({\text{O}}_{\text{Te}}{\text{-Te}}_{\text{Cd}}\right)$ complex. This complex is energeticall…

[Phys. Rev. B 93, 184103] Published Mon May 16, 2016

]]>We extend the nested sampling algorithm to simulate materials under periodic boundary and constant pressure conditions, and show how it can be used to determine the complete equilibrium phase diagram for a given potential energy function, efficiently and in a highly automated fashion. The only input…

[Phys. Rev. B 93, 174108] Published Fri May 13, 2016

]]>Using first-principles calculations based on density functional theory, we have studied the mechanical, electronic, and magnetic properties of Heusler alloys, namely, ${\mathrm{Ni}}_{2}BC$ and ${\mathrm{Co}}_{2}BC$ ($B$ = Sc, Ti, V, Cr, and Mn as well as Y, Zr, Nb, Mo, and Tc; $C$ = Ga and Sn). On the basis of electronic structure (de…

[Phys. Rev. B 93, 184102] Published Fri May 13, 2016

]]>To achieve a fundamental understanding of the multiferroic behavior and electronic properties of intrinsic vacancies in $\mathrm{BiFe}{\mathrm{O}}_{3}$, here we performed first-principles calculations based on hybrid Hartree-Fock density functional theories, which can accurately describe defect electronic structures. Oxygen…

[Phys. Rev. B 93, 174107] Published Thu May 12, 2016

]]>We propose a method to measure the hyperfine vectors between a nitrogen-vacancy (NV) center and an environment of interacting nuclear spins. Our protocol enables the generation of tunable electron-nuclear coupling Hamiltonians while suppressing unwanted internuclear interactions. In this manner, eac…

[Phys. Rev. B 93, 174104] Published Tue May 10, 2016

]]>Hydrogen sulfide $\left({\mathrm{H}}_{2}\mathrm{S}\right)$ was studied by x-ray synchrotron diffraction and Raman spectroscopy up to 150 GPa at 180–295 K and by quantum-mechanical variable-composition evolutionary simulations. The experiments show that ${\mathrm{H}}_{2}\mathrm{S}$ becomes unstable with respect to formation of compounds with different structur…

[Phys. Rev. B 93, 174105] Published Tue May 10, 2016

]]>Premelting or virtual melting was proposed previously as an important deformation mechanism for high strain-rate loading. However, two questions remain outstanding: how premelting occurs exactly, and whether it plays a role in plastic deformation independent of, parasitic on, or synergetic with, dis…

[Phys. Rev. B 93, 174106] Published Tue May 10, 2016

]]>Limit-periodic structures are well ordered but nonperiodic, and hence have nontrivial vibrational modes. We study a ball and spring model with a limit-periodic pattern of spring stiffnesses and identify a set of extended modes with arbitrarily low participation ratios, a situation that appears to be…

[Phys. Rev. B 93, 174102] Published Mon May 09, 2016

]]>Τhe magnetoelectric $\mathrm{ZnC}{\mathrm{r}}_{2}\mathrm{S}{\mathrm{e}}_{4}$ spinel, with space group $Fd\overline{3}m$, undergoes a reversible first-order structural transition initiating at 17 GPa, as revealed by our high-pressure x-ray diffraction studies at room temperature. We tentatively assign the high-pressure modification to an $A\mathrm{M}{\mathrm{o}}_{2}{\mathrm{S}}_{4}$-type phase, a …

[Phys. Rev. B 93, 174103] Published Mon May 09, 2016

]]>The origin of ferroelectric polarization in tetragonal tungsten-bronze- (TTB-) type oxide strontium barium niobate (SBN) is investigated using first-principles density functional calculations. We study in particular the relationship between the polarization and the cation and vacancy ordering on alk…

[Phys. Rev. B 93, 180101(R)] Published Mon May 09, 2016

]]>In a ferroelectric helimagnetic phase of a spin-driven multiferroic, ${\mathrm{CuFeO}}_{2}$, we find irreversibly additive evolution of electric polarization $P$ induced by sweeping magnetic field $H$ under an applied electric field $E$, despite a large coercive electric field in the phase. From the unpolarized neutron d…

[Phys. Rev. B 93, 174101] Published Tue May 03, 2016

]]>We demonstrate that the melting points and other thermodynamic quantities of the alkali metals can be calculated based on static crystalline properties. To do this we derive analytic interatomic potentials for the alkali metals fitted precisely to cohesive and vacancy energies, elastic moduli, the l…

[Phys. Rev. B 93, 184101] Published Mon May 02, 2016

]]>We introduce an algorithm for the reconstruction of the complex transmission function of a specimen using segmented detectors in scanning transmission electron microscopy geometry. The phase of the transmission function can be related to magnetic and electric fields within the specimen and is sensit…

[Phys. Rev. B 93, 134116] Published Wed Apr 27, 2016

]]>Oxygen vacancies in ${\mathrm{LaAlO}}_{3}$ (LAO) play an important role in the formation of the two-dimensional electron gas observed at the ${\mathrm{LaAlO}}_{3}\text{/}{\mathrm{SrTiO}}_{3}$ interface and affect the performance of MOSFETs using LAO as a gate dielectric. However, their spectroscopic properties are still poorly understood, which hamper…

[Phys. Rev. B 93, 134114] Published Mon Apr 25, 2016

]]>A formalism for the vacancy formation energies in random alloys within the single-site mean-filed approximation, where vacancy-vacancy interaction is neglected, is outlined. It is shown that the alloy configurational entropy can substantially reduce the concentration of vacancies at high temperature…

[Phys. Rev. B 93, 134115] Published Mon Apr 25, 2016

]]>Segregation-induced structural transitions in metallic grain boundaries are studied with hybrid atomistic Monte Carlo/molecular dynamics simulations using Cu-Zr as a model system, with a specific emphasis on understanding the effect of grain boundary character. With increasing global composition, th…

[Phys. Rev. B 93, 134113] Published Fri Apr 22, 2016

]]>The effect of external mechanical fields on relaxor $0.94\left(\mathrm{N}{\mathrm{a}}_{1/2}\mathrm{B}{\mathrm{i}}_{1/2}\right)\mathrm{Ti}{\mathrm{O}}_{3}\text{\u2212}0.06\mathrm{BaTi}{\mathrm{O}}_{3}$ was investigated by means of temperature- and stress-dependent dielectric constant measurements between 223 and 673 K. Analogous to previous investigations that showed an electric-field-induced ferroelectric long-ran…

[Phys. Rev. B 93, 134111] Published Wed Apr 20, 2016

]]>We studied the microscopic mechanism of the paraelectric-ferroelectric (PE-FE) phase transition of ${\mathrm{CsH}}_{2}{\mathrm{PO}}_{4}$ (CDP) by means of first-principles electronic structure calculations. The calculated structural parameters in the PE and FE phases as well as the total spontaneous polarization ${P}_{s}$ obtained with…

[Phys. Rev. B 93, 134112] Published Wed Apr 20, 2016

]]>High-resolution single crystal neutron diffraction measurements are presented probing the magnetostructural response to uniaxial pressure in the iron pnictide parent system ${\mathrm{BaFe}}_{2}{\mathrm{As}}_{2}$. Scattering data reveal a strain-activated, anisotropic broadening of nuclear Bragg reflections, which increase upon c…

[Phys. Rev. B 93, 144118] Published Wed Apr 20, 2016

]]>High-pressure solid-state transformations at high strain rates are usually observed after the fact, either during static holding or after unloading, or inferred from interferometry measurements of the sample surface. The emergence of femtosecond x-ray diffraction techniques provides insight into the…

[Phys. Rev. B 93, 144119] Published Wed Apr 20, 2016

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