Magnetoelectric coupling phenomena in ${\mathrm{EuTiO}}_{3}$ are of considerable fundamental interest and are also understood to be key to reported multiferroic behavior in strained films, which exhibit distinctly different properties to the bulk. Here, the magnetoelastic coupling of ${\mathrm{EuTiO}}_{3}$ is investigated by reson…

[Phys. Rev. B 93, 054108] Published Wed Feb 10, 2016

]]>A three-dimensional kinetic Monte Carlo (KMC) model has been developed and used to simulate the microstructure and growth morphology of cubic transition metal nitride (TMN) thin films deposited by reactive magnetron sputtering. Results are presented for the case of stoichiometric TiN, chosen as a re…

[Phys. Rev. B 93, 064107] Published Wed Feb 10, 2016

]]>We demonstrate a new level of precision in measuring melting temperatures at high pressure using laser flash heating in a diamond cell followed by an analysis using scanning electron microscopy and focused ion beam milling. The new measurements on tantalum put unprecedented constraints on its highly…

[Phys. Rev. B 93, 054107] Published Tue Feb 09, 2016

]]>We have investigated atomic dynamics of caged compound ${\mathrm{LaRu}}_{2}{\mathrm{Zn}}_{20}$ by the measurements of specific heat $C$ and inelastic x-ray scattering (IXS). The lattice part of the specific heat ${C}_{\mathrm{lat}}$ divided by ${T}^{3},{C}_{\mathrm{lat}}/{T}^{3}$, shows a broad peak at around 15 K, which is reproduced by two Einstein modes with characteri…

[Phys. Rev. B 93, 064105] Published Tue Feb 09, 2016

]]>The high-pressure behavior of $\mathrm{C}{\mathrm{e}}_{2}{\mathrm{O}}_{3}$ was studied using angle-dispersive x-ray diffraction to 70 GPa and compared with that of $\mathrm{Ce}{\mathrm{O}}_{2}$. Up to the highest pressure $\mathrm{C}{\mathrm{e}}_{2}{\mathrm{O}}_{3}$ remains in the hexagonal phase (space group 164, $P\overline{3}2/m1)$ typical for the lanthanide sesquioxides. A theoretically predicted phase insta…

[Phys. Rev. B 93, 064106] Published Tue Feb 09, 2016

]]>A structural phase transition has been discovered in the synthetic tetrahedrite ${\mathrm{Cu}}_{12}{\mathrm{Sb}}_{4}{\mathrm{S}}_{13}$ at approximately 88 K. Upon cooling, the material transforms from its known cubic symmetry to a tetragonal unit cell that is characterized by an in-plane ordering that leads to a doubling of the unit cell volu…

[Phys. Rev. B 93, 064104] Published Mon Feb 08, 2016

]]>A theory for the epitaxial growth of Au on ${\mathrm{MoS}}_{2}$ is developed and analyzed. The theory combines continuum linear elasticity theory with density functional theory to analyze epitaxial growth in this system. It is demonstrated that if one accounts for interfacial energies and strains, the presence of m…

[Phys. Rev. B 93, 054106] Published Fri Feb 05, 2016

]]>The presence of stacking fault tetrahedra (SFTs) in face-centered-cubic metals substantially modifies the material response to external loading. These defects are extremely stable with increasing energetic stability as they grow in size. At the sizes visible within a transmission electron microscope…

[Phys. Rev. B 93, 054105] Published Thu Feb 04, 2016

]]>Ruthenium hydride was synthesized at a hydrogen pressure of about 14 GPa in a diamond-anvil cell. Energy-dispersive x-ray diffraction was used to monitor the ruthenium crystal structure as a function of hydrogen pressure up to 30 GPa. The hydride formation was accompanied by phase transition from th…

[Phys. Rev. B 93, 064103] Published Thu Feb 04, 2016

]]>Pair distribution functions of ferroelectric $x{\mathrm{BiScO}}_{3}\text{\u2212}\left(1-x\right){\mathrm{PbTiO}}_{3}$, obtained from neutron total scattering data, were examined and modeled utilizing the reverse Monte Carlo technique to depict exclusively the local structure of this compound throughout its reported morphotropic phase boundary (MPB). M…

[Phys. Rev. B 93, 064102] Published Wed Feb 03, 2016

]]>The influence of a small amount of niobium ions (0.6 mol% $\mathrm{N}{\mathrm{b}}_{2}{\mathrm{O}}_{5}$) introduced into $\mathrm{PbZr}{\mathrm{O}}_{3}$ single crystals on the structural, dielectric, optical, and electromechanical properties was studied. The main goal was to search for the influence of this doping on the phase transition sequence. It was found th…

[Phys. Rev. B 93, 054104] Published Tue Feb 02, 2016

]]>Manganese fluoride $\left({\mathrm{MnF}}_{2}\right)$ with the tetragonal rutile-type structure has been studied using a synchrotron angle-dispersive powder x-ray diffraction and Raman spectroscopy in a diamond anvil cell up to 60 GPa at room temperature combined with first-principles density functional calculations. The exper…

[Phys. Rev. B 93, 054101] Published Mon Feb 01, 2016

]]>Compression of arsenolite has been studied from a joint experimental and theoretical point of view. Experiments on this molecular solid at high pressures with different pressure-transmitting media have been interpreted thanks to *state-of-the-art ab initio* calculations. Our results confirm arsenolite…

[Phys. Rev. B 93, 054102] Published Mon Feb 01, 2016

]]>By decoupling thermal equilibrium conditions in shock loaded porous materials, two regimes resulting in two-zone Hugoniot are revealed, specifically, a stable low-pressure regime characterized by achieving interphase temperature equilibrium and a metastable high-pressure regime. Porous materials, re…

[Phys. Rev. B 93, 054103] Published Mon Feb 01, 2016

]]>Using path integral Monte Carlo (PIMC) and density functional molecular dynamics (DFT-MD) simulation methods, we compute a coherent equation of state (EOS) of nitrogen that spans the liquid, warm dense matter (WDM), and plasma regimes. Simulations cover a wide range of density-temperature space, $1.5\dots $

[Phys. Rev. B 93, 064101] Published Mon Feb 01, 2016

]]>Raman spectroscopy and powder x-ray diffraction methods have been used to characterize a novel phase of nitrogen which forms on compression from ambient pressure at low temperatures. The new, $\lambda $, phase exhibits an exceptionally wide range of pressure stability from below 1 to 140 GPa, overlapping nin…

[Phys. Rev. B 93, 024113] Published Fri Jan 29, 2016

]]>The mechanical loss (${Q}^{-1}$) intrinsic to amorphous oxides is the limiting factor for sensitive, high-precision gravitational wave detectors and optical devices. Recent experimental work suggests that doping amorphous tantala with titania reduces ${Q}^{-1}$, however, the physical processes underlying this red…

[Phys. Rev. B 93, 014105] Published Mon Jan 25, 2016

]]>We study the nonequilibrium dynamics of the linear-to-zigzag structural phase transition exhibited by an ion chain confined in a trap with periodic boundary conditions. The transition is driven by reducing the transverse confinement at a finite quench rate, which can be accurately controlled. This r…

[Phys. Rev. B 93, 014106] Published Mon Jan 25, 2016

]]>We introduce a phenomenological theory of dislocation motion appropriate for two-dimensional lattices. A coarse grained description is proposed that involves as primitive variables local lattice rotation and Burgers vector densities along distinguished slip systems of the lattice. We then use symmet…

[Phys. Rev. B 93, 014107] Published Mon Jan 25, 2016

]]>Surface waves are often excited by interdigitated transducers consisting of many nanostrips attached on a substrate, and it has been recognized that the mass and stiffness of the attached nanostrips affect surface-wave resonances to some extent. Here, we reveal the more noticeable influence of the i…

[Phys. Rev. B 93, 024112] Published Fri Jan 22, 2016

]]>The Wang-Landau Monte Carlo algorithm is implemented within an effective Hamiltonian approach and applied to ${\mathrm{BaTiO}}_{3}$ bulk. The density of states obtained by this approach allows a highly accurate and straightforward calculation of various thermodynamic properties, including phase transition temperatu…

[Phys. Rev. B 93, 014104] Published Thu Jan 21, 2016

]]>We develop a procedure to determine the portion of exact Hartree-Fock exchange interaction contained in a hybrid density functional to treat the range of electronic correlation governing the physics of a system as a function of a thermodynamical parameter. This includes systems that depend on physic…

[Phys. Rev. B 93, 024111] Published Wed Jan 20, 2016

]]>The motion of [100](010) screw dislocations via a kink-pair mechanism is investigated in high-pressure ${\mathrm{MgSiO}}_{3}$ perovskite by means of atomistic calculations and an elastic interaction model for kink nucleation. Atomistic calculations based on the nudged elastic band method provide the Peierls potenti…

[Phys. Rev. B 93, 014103] Published Tue Jan 19, 2016

]]>Oxygen octahedra tilting is a common structural phenomenon in perovskites and has been subject of intensive studies, particularly in rhombohedral $\mathrm{Pb}\left(\mathrm{Zr},\mathrm{Ti}\right){\mathrm{O}}_{3}$ (PZT). Early reports suggest that the tilted octahedra may strongly affect the domain switching behavior as well as the dielectric and piezoel…

[Phys. Rev. B 93, 014102] Published Fri Jan 15, 2016

]]>As titanium is a highly utilized metal for structural lightweighting, its phases, transformation pathways (transition states), and structures have scientific and industrial importance. Using a proper solid-state nudged elastic band method employing two climbing images combined with density functiona…

[Phys. Rev. B 93, 020104(R)] Published Fri Jan 15, 2016

]]>The response of small-grained metals to mechanical stress is investigated by a theoretical study of the elementary mechanisms occurring during the shear-coupled migration of grain boundaries (GB). Investigating a model $\mathrm{\Sigma}17\left(410\right)$ GB in a copper bicrystal, both $\langle 110\rangle $ and $\langle 100\rangle $ GB migration modes are st…

[Phys. Rev. B 93, 024109] Published Fri Jan 15, 2016

]]>Compresed BiTeBr has been studied from a joint experimental and theoretical perspective. Room-temperature x-ray diffraction, Raman scattering, and transport measurements at high pressures have been performed in this layered semiconductor and interpreted with the help of *ab initio* calculations. A rev…

[Phys. Rev. B 93, 024110] Published Fri Jan 15, 2016

]]>We have investigated nonequilibrium properties of proper uniaxial ${\mathrm{Sn}}_{2}{\mathrm{P}}_{2}{\left({\mathrm{Se}}_{x}{\mathrm{S}}_{1-x}\right)}_{6}$ ferroelectrics with the type II incommensurate phase above Lifshitz point ${x}_{\mathrm{LP}}\sim 0.28$. We performed measurements of dielectric susceptibility in cooling and heating regimes with the rate ranging 0.002–0.1 K/min, as well a…

[Phys. Rev. B 93, 014101] Published Thu Jan 14, 2016

]]>We show that the pressure-induced metal-insulator transition (MIT) in ${\mathrm{LaMnO}}_{3}$ is fundamentally different from the Mott-Hubbard transition and is percolative in nature, with the measured resistivity obeying the percolation scaling laws. Using the Gutzwiller method to treat correlation effects in a mod…

[Phys. Rev. B 93, 024107] Published Wed Jan 13, 2016

]]>Using synchrotron and neutron diffraction measurements, we find a low-temperature orthorhombic phase in vanadium spinel ${\mathrm{FeV}}_{2}{\mathrm{O}}_{4}$. The orbital order of ${\mathrm{V}}^{3+}$ ions with tetragonal normal modes occurs at 68 K, and this leads to an appearance of the pseudotetragonal phase at a noncollinear ferrimagnetic tra…

[Phys. Rev. B 93, 024108] Published Wed Jan 13, 2016

]]>Hydrogen sulfides have recently received a great deal of interest due to the record high-${T}_{c}$ of up to 203 K observed on strong compression of H${}_{2}$S . In this paper, a joint theoretical and experimental study is presented to characterize the dissociation products of compressed H${}_{2}$S , which is essential to understand its complex superconducting states. Based on the results here, the authors found H${}_{2}$S partially decomposes into S + H${}_{3}$S + H${}_{4}$S${}_{3}$ above 27 GPa, and H${}_{4}$S${}_{3}$ emerges as the major component at around 66 GPa. Interestingly, x-ray diffraction (XRD) experiments observed a small fraction of H${}_{3}$S and residual H${}_{2}$S at least up to 140 GPa, which are believed to be responsible for the two superconducting states observed in experiments. This paper provides the first XRD evidence on the existence of H${}_{3}$S at high pressure from the decomposition of H${}_{2}$S.

[Phys. Rev. B 93, 020103(R)] Published Mon Jan 11, 2016

]]>The complex nature of the structural disorder in the lead-free ferroelectric $\mathrm{N}{\mathrm{a}}_{1/2}\mathrm{B}{\mathrm{i}}_{1/2}\mathrm{Ti}{\mathrm{O}}_{3}$ has a profound impact on the perceived global structure and polar properties. In this paper, we have investigated the effect of electric field and temperature on the local structure around the Bi and Ti atoms…

[Phys. Rev. B 93, 024106] Published Mon Jan 11, 2016

]]>The Kibble-Zurek mechanism demands an initial adiabatic stage before an impulse stage to have a frozen correlation length that generates topological defects in a cooling phase transition. Here we study such a driven critical dynamics but with an initial condition that is near the critical point and …

[Phys. Rev. B 93, 024103] Published Fri Jan 08, 2016

]]>It is generally accepted that nuclear quantum effects (NQEs) trigger the transition to the nonmolecular form of ice under increasing pressure. This picture is challenged in salty ice, where Raman scattering measurements up to 130 GPa of molecular ice VII containing NaCl or LiCl impurities show that …

[Phys. Rev. B 93, 024104] Published Fri Jan 08, 2016

]]>Flexoelectricity is evolution of a macroscopic polarization due to a strain *gradient*. We present a molecular dynamics study of flexoelectricity in the cubic ionic MgO periclase phase. Using an effective interaction force field with polarizable oxygen atoms and applying it to an inhomogeneously strai…

[Phys. Rev. B 93, 024105] Published Fri Jan 08, 2016

]]>Through a combination of modeling and density functional theory calculations, the authors solve the structure of the only known quasicrystalline oxide, Ba-Ti-O, and introduce a new crystal-chemistry motif that explains all previously unsolved ultrathin Ba-Ti-O structures.

[Phys. Rev. B 93, 020101(R)] Published Thu Jan 07, 2016

]]>Probing the ferroelectricity at the nanometer scale is of particular interest for a wide range of applications. In this Rapid Communication, the structural distortion of ${\mathrm{BaTiO}}_{3}$ (BTO) is studied in its ferroelectric (rhombohedral and tetragonal), and paraelectric phases from the O $K$ near edge structu…

[Phys. Rev. B 93, 020102(R)] Published Thu Jan 07, 2016

]]>A first-principles nonequilibrium molecular dynamics (NEMD) study employing the color-diffusion algorithm has been conducted to obtain the bulk ionic conductivity and the diffusion constant of gadolinium-doped cerium oxide (GDC) in the 850–1150 K temperature range. Being a slow process, ionic diffus…

[Phys. Rev. B 93, 024102] Published Wed Jan 06, 2016

]]>The ordered double-perovskite $\mathrm{S}{\mathrm{r}}_{2}\mathrm{FeMo}{\mathrm{O}}_{6}$ (SFMO) possesses remarkable room-temperature low-field colossal magnetoresistivity and transport properties which are related, at least in part, to combined structural and magnetic instabilities that are responsible for a cubic-tetragonal phase transition near…

[Phys. Rev. B 93, 024101] Published Tue Jan 05, 2016

]]>We present a set of three-body interaction models based on the Slater-Kirkwood (SK) potential that are suitable for the study of the energy, structural, and elastic properties of solid ${}^{4}\mathrm{He}$ at high pressure. Our effective three-body potentials are obtained from the fit to total energies and atomic fo…

[Phys. Rev. B 92, 224113] Published Thu Dec 31, 2015

]]>${\mathrm{KH}}_{2}{\mathrm{PO}}_{4}$ (KDP) belongs to the class of hydrogen-bonded ferroelectrics, whose paraelectric to ferroelectric phase transition is driven by the ordering of the protons in the hydrogen bonds. We demonstrate that forbidden reflections of KDP, when measured at an x-ray absorption edge, are highly sensitive …

[Phys. Rev. B 92, 214116] Published Wed Dec 30, 2015

]]>Iron-chromium alloys, the base components of various stainless steel grades, have numerous technologically and scientifically interesting properties. However, these features are not yet sufficiently understood to allow their full exploitation in technological applications. In this work, we investiga…

[Phys. Rev. B 92, 214113] Published Mon Dec 28, 2015

]]>Barium cerate (${\mathrm{BaCeO}}_{3}$) is a well-known ionic conductor of both hydrogen and oxygen. In applications, it is frequently doped (for instance with Y) to increase stability and promote diffusion. However, the effects of doping and native defects are not fully understood. Computational studies have been s…

[Phys. Rev. B 92, 214114] Published Mon Dec 28, 2015

]]>Switching, i.e., polarization reversal, of ferroelectric P(VDF-TrFE) thin films has been investigated in a wide range of applied electric field and temperature. The measured polarization transients can be quantitatively described by a compressed exponential function as originally formulated by Kolmo…

[Phys. Rev. B 92, 214115] Published Mon Dec 28, 2015

]]>We consider the properties of charged domain walls in ferroelectrics as a quantum problem. This includes determination of self-consistent attracting 1D potential for compensating charge carriers, the number and positions of discrete energy levels in this potential, dependencies on the ferroelectric …

[Phys. Rev. B 92, 214112] Published Wed Dec 23, 2015

]]>There is great interest in lead-free $\left(\mathrm{B}{\mathrm{a}}_{0.85}\mathrm{C}{\mathrm{a}}_{0.15}\right)\left(\mathrm{T}{\mathrm{i}}_{0.90}\mathrm{Z}{\mathrm{r}}_{0.10}\right){\mathrm{O}}_{3}$ (15/10BCTZ) because of its exceptionally large piezoelectric response [Liu and Ren, Phys. Rev. Lett. **103**, 257602 (2009)]. In this paper, we have analyzed the nature of: (i) crystallographic phase coexistence at room temperature, (ii…

[Phys. Rev. B 92, 224112] Published Wed Dec 23, 2015

]]>Inelastic scattering and carrier capture by defects in semiconductors are the primary causes of hot-electron-mediated degradation of power devices, which holds up their commercial development. At the same time, carrier capture is a major issue in the performance of solar cells and light-emitting dio…

[Phys. Rev. B 92, 214111] Published Mon Dec 21, 2015

]]>The identification of defect levels from photoluminescence spectroscopy is a useful but challenging task. Density-functional theory (DFT) is a highly valuable tool to this aim. However, the semilocal approximations of DFT that are affected by a band gap underestimation are not reliable to evaluate d…

[Phys. Rev. B 92, 224111] Published Mon Dec 21, 2015

]]>Barlowite ${\mathrm{Cu}}_{4}{\left(\mathrm{OH}\right)}_{6}\mathrm{FBr}$ is a newly found mineral containing ${\mathrm{Cu}}^{2+}$ kagome planes. Despite similarities in many aspects to herbertsmithite ${\mathrm{Cu}}_{3}\mathrm{Zn}{\left(\mathrm{OH}\right)}_{6}{\mathrm{Cl}}_{2}$, the well-known quantum spin liquid (QSL) candidate, intrinsic barlowite turns out not to be a QSL, possibly due to the presence of ${\mathrm{Cu}}^{2+}$ ions in between…

[Phys. Rev. B 92, 220102(R)] Published Fri Dec 18, 2015

]]>Indentation-induced plastic deformation of amorphous silicon (a-Si) thin films was studied by *in situ* Raman imaging of the deformed contact region of an indented sample, employing a Raman spectroscopy-enhanced instrumented indentation technique. Quantitative analyses of the generated *in situ* Raman m…

[Phys. Rev. B 92, 214110] Published Thu Dec 17, 2015

]]>The high-pressure melting curve of titanium has been studied up to 120 GPa and $\sim 3500$ K using both laser-heated diamond anvil cells and *ab initio* molecular dynamic simulations. Several theoretical and experimental melting diagnostics, including x-ray diffraction, are tested and compared. Using the mo…

[Phys. Rev. B 92, 224110] Published Thu Dec 17, 2015

]]>The characteristic structural off-centering of ${\mathrm{Pb}}^{2+}$ in oxides, associated with its $6{s}^{2}$ lone pair, allows it to play a dominant role in polar materials, and makes it a somewhat ubiquitous component of ferroelectrics. In this work, we examine the compounds ${\mathrm{Sr}}_{0.9}{\mathrm{Sn}}_{0.1}{\mathrm{TiO}}_{3}$ and ${\mathrm{Ba}}_{0.79}{\mathrm{Ca}}_{0.16}{\mathrm{Sn}}_{0.05}{\mathrm{TiO}}_{3}$ usi…

[Phys. Rev. B 92, 214109] Published Wed Dec 16, 2015

]]>Compressed hydrides of the heavy group-15 elements Bi and Sb are investigated using *ab initio* methods. While the hydrides of Bi and Sb are known to be quite unstable at one atmosphere, our calculations predict that they can be stabilized at high pressures. Thus, at the composition of ${X\mathrm{H}}_{3}$ ($X=\text{Bi}$ or Sb…

[Phys. Rev. B 92, 224109] Published Wed Dec 16, 2015

]]>The complexity associated with local structures continues to pose challenges with regard to the understanding of the structure-property relationship in $\mathrm{N}{\mathrm{a}}_{1/2}\mathrm{B}{\mathrm{i}}_{1/2}\mathrm{Ti}{\mathrm{O}}_{3}$-based lead-free piezoceramics. $\left(1-x\right)\mathrm{N}{\mathrm{a}}_{1/2}\mathrm{B}{\mathrm{i}}_{1/2}\mathrm{Ti}{\mathrm{O}}_{3}-\left(x\right)\mathrm{BaTi}{\mathrm{O}}_{3}$ is an extensively studied system because of its interesting piezoelectri…

[Phys. Rev. B 92, 214107] Published Mon Dec 14, 2015

]]>Design of novel artificial materials based on ferroelectric perovskites relies on the basic principles of electrostatic coupling and in-plane lattice matching. These rules state that the out-of-plane component of the electric displacement field and the in-plane components of the strain are preserved…

[Phys. Rev. B 92, 214108] Published Mon Dec 14, 2015

]]>Epitaxial films of $\mathrm{C}{\mathrm{o}}_{x}\mathrm{M}{\mathrm{n}}_{y}\mathrm{G}{\mathrm{e}}_{z}$ grown on Ge (111) substrates by molecular-beam-epitaxy techniques have been investigated as a continuous function of composition using combinatorial synchrotron x-ray diffraction (XRD) and x-ray fluorescence (XRF) spectroscopy techniques. A high-resolution ternary epitax…

[Phys. Rev. B 92, 224108] Published Mon Dec 14, 2015

]]>We derived a formula to describe the stimulated Brillouin spectral shape in crystals for various temperatures ranging from room temperature to liquid-helium temperature. We modeled a sample as a one-dimensional system with a finite thickness in which the optically induced phonon propagates, partly i…

[Phys. Rev. B 92, 214105] Published Fri Dec 11, 2015

]]>The lithium-carbon binary system possesses a broad range of chemical compounds, which exhibit fascinating chemical bonding characteristics, which give rise to diverse and technologically important properties. While lithium carbides with various compositions have been studied or suggested previously,…

[Phys. Rev. B 92, 214106] Published Fri Dec 11, 2015

]]>We present a class of Rashba systems in hexagonal semiconducting compounds, where an electrical control over spin-orbital texture is provided by their bulk ferroelectricity. Our first-principles calculations reveal a number of such materials with large Rashba coefficients. We, furthermore, show that…

[Phys. Rev. B 92, 220101(R)] Published Thu Dec 10, 2015

]]>Using the atomic density function theory (ADFT), we examine the point defect absorption at [110] symmetrical tilt grain boundaries in body-centered cubic iron. It is found that the sink strength strongly depends on misorientation angle. We also show that the ADFT is able to reproduce reasonably well…

[Phys. Rev. B 92, 224106] Published Thu Dec 10, 2015

]]>Using first-principles mean-field alloy theory, we calculate the vacancy formation energies of the face-centered-cubic Pd-Ag alloys as a function of chemical composition. The effect of Fermi surface topological transition on the composition dependence of the vacancy formation energies is detectable …

[Phys. Rev. B 92, 224107] Published Thu Dec 10, 2015

]]>The results of a comprehensive and systematic *ab initio* based ground-state search for the structural arrangement of oxygen vacancies in rutile phase ${\mathrm{TiO}}_{2}$ provide new insights into their memristive properties. We find that O vacancies tend to form planar arrangements which relax into structures exhib…

[Phys. Rev. B 92, 214104] Published Wed Dec 09, 2015

]]>Single crystals of $\mathrm{YAl}{\mathrm{O}}_{3}$ doped with Ce have been studied by electron paramagnetic resonance (EPR) at the 9.4 and 34 GHz microwave bands. Besides the single-ion $\mathrm{C}{\mathrm{e}}^{3+}$ spectrum, measurements have revealed many satellite lines which belong to the $\mathrm{C}{\mathrm{e}}^{3+}\text{\u2212}\mathrm{C}{\mathrm{e}}^{3+}$ pair centers. Their spectra have been fitted by…

[Phys. Rev. B 92, 224105] Published Wed Dec 09, 2015

]]>Detailed quantitative measurement of surface dynamics during thin film growth is a major experimental challenge. Here x-ray photon correlation spectroscopy with coherent hard x rays is used in a grazing-incidence small-angle x-ray scattering (i.e., Co-GISAXS) geometry as a tool to investigate nanosc…

[Phys. Rev. B 92, 214102] Published Tue Dec 08, 2015

]]>We use first-principles calculations to investigate the lattice properties of group-IV monochalcogenides. These include static dielectric permittivity, elastic and piezoelectric tensors. For the monolayer, it is found that the static permittivity, besides acquiring a dependence on the interlayer dis…

[Phys. Rev. B 92, 214103] Published Tue Dec 08, 2015

]]>We present high-energy x-ray diffraction data under applied pressures up to $p=29\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, neutron diffraction measurements up to $p=1.1\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, and electrical resistance measurements up to $p=5.9\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, on ${\mathrm{SrCo}}_{2}{\mathrm{As}}_{2}$. Our x-ray diffraction data demonstrate that there is a first-order transition between the tetragon…

[Phys. Rev. B 92, 224103] Published Tue Dec 08, 2015

]]>${\mathrm{TaS}}_{2}$ is a transition-metal dichalcogenide having an exceptionally rich phase diagram, which includes exotic phenomena such as a charge density wave. We analyzed the structure, bonding, ground state, and dynamical stability of $1T,2H$, and $3R$ phases of ${\mathrm{TaS}}_{2}$, and a commensurate charge density wave phas…

[Phys. Rev. B 92, 224104] Published Tue Dec 08, 2015

]]>A collaboration of researchers from France, Germany, and Spain present a comprehensive study of the structure and motion of dislocations in a technologically important ferroelectric KNbO${}_{3}$ perovskite.

[Phys. Rev. B 92, 214101] Published Mon Dec 07, 2015

]]>We present melting curves of aluminum, copper, and nickel calculated on the basis of a quasiharmonic approximation. The dependence of a phonon density of states on electron temperature is taken into account for both thermodynamic properties and a mean square displacement of atoms. Linear expansion c…

[Phys. Rev. B 92, 224102] Published Mon Dec 07, 2015

]]>A unified treatment of coupled optical and acoustic phonons in piezoelectric cubic materials is presented whereby the lattice displacement vector and the internal ionic displacement vector are found simultaneously. It is shown that phonon couplings exist in pairs only; either between the electric po…

[Phys. Rev. B 92, 224101] Published Tue Dec 01, 2015

]]>The phase diagram and the relationship between the crystal coherence length and electrical response of ${\mathrm{Pb}[\left({\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}\right)}_{1-x}{\mathrm{Ti}}_{x}]{\mathrm{O}}_{3}$ (PMN-$x\mathrm{PT}$) near the morphotropic phase boundary (MPB) have been precisely investigated using a single crystal with a Ti composition gradient by synchrotron x-ray diffraction…

[Phys. Rev. B 92, 174121] Published Mon Nov 30, 2015

]]>YbBiPt is a heavy-fermion compound possessing significant short-range antiferromagnetic correlations below a temperature of ${T}^{\text{*}}=0.7\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, fragile antiferromagnetic order below ${T}_{\mathrm{N}}=0.4\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, a Kondo temperature of ${T}_{\mathrm{K}}\approx 1\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, and crystalline-electric-field splitting on the order of $E/{k}_{\mathrm{B}}=1\text{\u2013}10\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Whereas the compound …

[Phys. Rev. B 92, 184111] Published Mon Nov 30, 2015

]]>Discovering materials that display a linear magnetoelectric (ME) effect at room temperature is a challenge. Such materials could facilitate devices based on the electric field control of magnetism. Here we present simple, chemically intuitive design rules to identify a class of bulk magnetoelectric …

[Phys. Rev. B 92, 184112] Published Mon Nov 30, 2015

]]>The potential of quarternary wurtzite ${\mathrm{TM}}_{x/2}{\mathrm{M}}_{x/2}{\mathrm{Al}}_{1-x}\mathrm{N}$ ($\mathrm{TM}=\text{Ti}$, Zr, Hf; $\mathrm{M}=\text{Mg}$, Ca, Zn) alloys for piezoelectric applications is investigated using first-principles calculations. All considered alloys show increased piezoelectric response compared to pure AlN, and competing with the best ternary system …

[Phys. Rev. B 92, 174119] Published Wed Nov 25, 2015

]]>The elastic energy functional of a system of discrete dislocation lines is well known from dislocation theory. In this paper, we demonstrate how the discrete functional can be used to systematically derive approximations which express the elastic energy in terms of dislocation densitylike variables …

[Phys. Rev. B 92, 174120] Published Wed Nov 25, 2015

]]>We report calculations of phonon dispersions of iron (Fe) at its $\gamma -\delta $ phase transition using a self-consistent *ab initio* lattice dynamical method in conjunction with an effective magnetic force approach via the antiferromagnetic approximation. Our results show that anharmonic phonon-phonon interactio…

[Phys. Rev. B 92, 184110] Published Tue Nov 24, 2015

]]>Density functional theory (DFT) calculations of 58 liquid elements at their triple point show that most metals exhibit near proportionality between the thermal fluctuations of the virial and the potential energy in the isochoric ensemble. This demonstrates a general “hidden” scale invariance of meta…

[Phys. Rev. B 92, 174116] Published Mon Nov 23, 2015

]]>A first-principles study of the $L{1}_{2}\phantom{\rule{4pt}{0ex}}{\text{Co}}_{3}(\text{Al},\text{W})$ phase was performed to assess phase stability at elevated temperature. Configurational degrees of freedom were treated with a cluster expansion and Monte Carlo simulations, while contributions to the free energy from vibrational excitations were determine…

[Phys. Rev. B 92, 174117] Published Mon Nov 23, 2015

]]>The thermodynamic compensation law describing an empirical linear relationship between activation enthalpy and activation entropy has seldom been validated for amorphous solids. Here molecular dynamics simulations reveal a well-defined enthalpy-entropy compensation rule in a metallic glass (MG) over…

[Phys. Rev. B 92, 174118] Published Mon Nov 23, 2015

]]>Molecular-dynamics simulations combined with a two-temperature model are used to study laser ablation in ${\text{Cu}}_{x}{\text{Zr}}_{1-x}$ $\left(x=0.33,0.50,0.67\right)$ metallic glasses as well as crystalline ${\text{CuZr}}_{2}$ in the ${\text{C11}}_{b}$ $\left({\text{MoSi}}_{2}\right)$ structure. Ablation thresholds are found to be $430\pm 10,450\pm 10,510\pm 10$, and $470\pm 10$ ${\mathrm{J}/\mathrm{m}}_{2}$ for a-${\text{Cu}}_{2}\text{Zr}$, a-C…

[Phys. Rev. B 92, 184108] Published Mon Nov 23, 2015

]]>This paper introduces a phase-field crystal (PFC) approach that couples the atomic-scale PFC density field to order parameters describing ferromagnetic and ferroelectric ordering, as well to a solute impurity field. This model extends the magnetic PFC model introduced by Faghihi *et al.* [N. Faghihi, …

[Phys. Rev. B 92, 184109] Published Mon Nov 23, 2015

]]>Molybdenum (Mo) is a body-centered-cubic (bcc) transition metal that has widespread technological applications. Although the bcc transition elements are used as test cases for understanding the behavior of metals under extreme conditions, the melting curves and phase transitions of these elements ha…

[Phys. Rev. B 92, 174114] Published Fri Nov 20, 2015

]]>A full understanding of the basic processes of grain boundary migration is a fundamental prerequisite for predictive models of microstructural evolution in polycrystalline materials in processing and in service. In a detailed study of the kinetics of a $\left[111\right]\mathrm{\Sigma}7$ symmetric tilt boundary, we have previ…

[Phys. Rev. B 92, 174115] Published Fri Nov 20, 2015

]]>The stress-induced martensitic transition in a Cu-Zn-Al shape memory alloy has been studied under three different driving conditions by using (i) a hard driving device which imposes a displacement rate on the sample heads, (ii) a soft driving device which imposes a loading rate on the sample, and (i…

[Phys. Rev. B 92, 184107] Published Fri Nov 20, 2015

]]>The structure and superfluid response of nanoscale size ${}^{4}\mathrm{He}$ clusters enclosed in spherical cavities are studied by computer simulations. The curved surface causes the formation of well-defined concentric shells, thus imparting to the system a very different structure from that of freestanding cluste…

[Phys. Rev. B 92, 174112] Published Thu Nov 19, 2015

]]>We measured the absolute lengths of three single-crystal silicon samples by means of an imaging Twyman-Green interferometer in the temperature range from 7 K to 293 K with uncertainties of about 1 nm. From these measurements we extracted the coefficient of thermal expansion with uncertainties on the…

[Phys. Rev. B 92, 174113] Published Thu Nov 19, 2015

]]>We have studied the temperature induced $0-\pi $ thermodynamic transition in Nb/PdNi/Nb superconductor/ferromagnetic/superconductor (SFS) heterostructures by microwave measurements of the superfluid density. We have observed a shift in the transition temperature with the ageing of the heterostructures, s…

[Phys. Rev. B 92, 184106] Published Thu Nov 19, 2015

]]>We derive a general theory of effective properties in metasolids based on phononic crystals with low frequency resonances. We demonstrate that in general these structures need to be described by means of a frequency-dependent and nonlocal anisotropic mass density, stiffness tensor and a third-rank c…

[Phys. Rev. B 92, 174110] Published Tue Nov 17, 2015

]]>The equilibrium structure and functional properties exhibited by brownmillerite oxides, a family of perovskite-derived structures with alternating layers of $B{\mathrm{O}}_{6}$ octahedra and $B{\mathrm{O}}_{4}$ tetrahedra, viz., ordered arrangements of oxygen vacancies, is dependent on a variety of competing crystal-chemistry fact…

[Phys. Rev. B 92, 174111] Published Tue Nov 17, 2015

]]>We present a multiphase-field theory for describing pattern formation in multidomain and/or multicomponent systems. The construction of the free energy functional and the dynamic equations is based on criteria that ensure mathematical and physical consistency. We first analyze previous multiphase-fi…

[Phys. Rev. B 92, 184105] Published Tue Nov 17, 2015

]]>Ultrafast laser irradiation can trigger anisotropically structured nanoscaled gratinglike arrangements of matter, the laser-induced periodic surface structures (LIPSSs). We demonstrate here that the formation of LIPSS is intrinsically related to the coherence of the laser field. Employing several te…

[Phys. Rev. B 92, 174109] Published Fri Nov 13, 2015

]]>Using first-principles evolutionary simulations, we have systematically investigated phase stability in the Hf-O system at pressure up to 120 GPa. New compounds ${\mathrm{Hf}}_{5}{\mathrm{O}}_{2},{\mathrm{Hf}}_{3}{\mathrm{O}}_{2}$, HfO, and ${\mathrm{HfO}}_{3}$ are discovered to be thermodynamically stable at certain pressure ranges. Two new high-pressure phases are found…

[Phys. Rev. B 92, 184104] Published Fri Nov 13, 2015

]]>By means of *ab initio* molecular dynamics calculations, the thermal evolution of vibrational properties in $\alpha $-U is studied at low temperature. The phase transition undergone by this material around 50 K was previously studied extensively using *ab initio* calculations in the framework of the linear resp…

[Phys. Rev. B 92, 174108] Published Wed Nov 11, 2015

]]>The melting curve of osmium up to a pressure $P$ of 500 GPa is obtained from an extensive suite of *ab initio* quantum molecular dynamics (QMD) simulations using the Z method. The *ab initio* $P=0$ melting point of Os is $3370\pm 75$ K; this range encompasses all of the available data in the literature and corro…

[Phys. Rev. B 92, 174105] Published Mon Nov 09, 2015

]]>Recent progress of high-pressure technology enables the synthesis of novel metal borides with diverse compositions and interesting properties. A precise characterization of these borides, however, is sometimes hindered by multiphase intergrowth and grain-size limitation in the synthesis process. Her…

[Phys. Rev. B 92, 174106] Published Mon Nov 09, 2015

]]>The properties of the interface between solid and melt are key to solidification and melting, as the interfacial free energy introduces a kinetic barrier to phase transitions. This makes solidification happen below the melting temperature, in out-of-equilibrium conditions at which the interfacial fr…

[Phys. Rev. B 92, 180102(R)] Published Mon Nov 09, 2015

]]>The isothermal compressibility of a general crystal is analyzed within classical density functional theory. Our approach can be used for homogeneous and unstrained crystals containing an arbitrarily high density of local defects. We start by coarse-graining the microscopic particle density and then …

[Phys. Rev. B 92, 184103] Published Mon Nov 09, 2015

]]>Previous studies have indicated that the figure of merit ($\mathit{ZT}$) of half-Heusler (HH) alloys with composition $M\mathrm{NiSn}$ ($M\phantom{\rule{0.16em}{0ex}}=\phantom{\rule{0.16em}{0ex}}\mathrm{Ti}$, Zr, or Hf) is greatly enhanced when the alloys contain a nano-scale full-Heusler (FH) $\mathrm{MN}{\mathrm{i}}_{2}\mathrm{Sn}$ second phase. However, the formation mechanism of the FHnanostructures in the HH matrix…

[Phys. Rev. B 92, 174102] Published Fri Nov 06, 2015

]]>Microscopic polar clusters can play an important role in the phase transition of ferroelectric perovskite oxides such as $\mathrm{BaTi}{\mathrm{O}}_{3}$, which have shown coexistence of both displacive and order-disorder dynamics, although their topological and dynamical characteristics are yet to be clarified. Here, we rep…

[Phys. Rev. B 92, 174103] Published Fri Nov 06, 2015

]]>Subpicosecond double-pulse laser ablation of metals is simulated using a hybrid model that combines classical molecular dynamics and an energy equation for free electrons. The key advantage of our model is the usage of the Helmholtz wave equation for the description of the laser energy absorption. A…

[Phys. Rev. B 92, 174104] Published Fri Nov 06, 2015

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