We investigate the behavior of sulfur vacancy defects, the most abundant type of intrinsic defect in monolayer ${\mathrm{MoS}}_{2}$, using first-principles calculations based on density functional theory. We consider the dependence of the isolated defect formation energy on the charge state and on uniaxial tensile …

[Phys. Rev. B 95, 014106] Published Tue Jan 17, 2017

]]>The $5d$-transition-metal pyrochlore oxide $\mathrm{C}{\mathrm{d}}_{2}\mathrm{R}{\mathrm{e}}_{2}{\mathrm{O}}_{7}$, which was recently suggested to be a prototype of the spin-orbit-coupled metal [Phys. Rev. Lett. **115**, 026401 (2015)], exhibits an inversion-symmetry-breaking (ISB) transition at 200 K and a subsequent superconductivity below 1 K at ambient pressure.…

[Phys. Rev. B 95, 020102(R)] Published Wed Jan 11, 2017

]]>The linear and nonlinear phononic interactions between an optically excited infrared (IR) or hyper-Raman mode and a driven Raman mode are computed for the ${d}^{0}\left({\mathrm{CaTiO}}_{3}\right)$ and ${d}^{1}\left({\mathrm{LaTiO}}_{3}\right)$ titanates within a first-principles density functional framework. We calculate the potential energy surface expanded …

[Phys. Rev. B 95, 024109] Published Wed Jan 11, 2017

]]>The impact of flexoelectric coupling on polarization reversal and space-charge variation in thin films of ferroelectric semiconductors has been studied theoretically. The relaxation-type Landau-Khalatnikov equation together with the Poisson equation and the theory of elasticity equations have been u…

[Phys. Rev. B 95, 014104] Published Tue Jan 10, 2017

]]>Materials physicists are increasingly coming to understand that domain walls in complex materials often have a life of their own. Far from being unwanted “defects”, they may have rich and interesting physics not available in the bulk material. Here, the authors use first-principles theoretical methods to consider ferroelectric domain walls in a promising family of corundum-derivative materials. Beyond studying issues of domain wall mobility and clarifying the factors that allow polarization reversal, the authors also identify an unusual set of domain-wall-specific couplings between polarization, magnetization, and chirality that they suggest may lead to new functionalities.

[Phys. Rev. B 95, 014105] Published Tue Jan 10, 2017

]]>Two quaternary Heusler alloys, equiatomic CuNiMnAl and CuNiMnSn, are studied using density functional theory to understand their tendency for atomic disorder on the lattice and the magnetic effects of disorder. Disordered structures with antisite defects of atoms of the same and different sublattice…

[Phys. Rev. B 95, 024108] Published Tue Jan 10, 2017

]]>The effect of pressure on the electronic properties and crystal structure in a mixed spinel ferrite $\mathrm{Z}{\mathrm{n}}_{0.2}\mathrm{M}{\mathrm{g}}_{0.8}\mathrm{F}{\mathrm{e}}_{2}{\mathrm{O}}_{4}$ was studied for the first time up to 48 GPa at room temperature using x-ray diffraction, Raman spectroscopy, and electrical transport measurements. The sample was cubic (spinel-type $Fd\stackrel{}{\mathrm{\dots}}$

[Phys. Rev. B 95, 024107] Published Mon Jan 09, 2017

]]>We formulate the problem of numerical analytic continuation in a way that lets us draw meaningful conclusions about the properties of the spectral function based solely on the input data. Apart from ensuring consistency with the input data (within their error bars) and the *a priori* and *a posteriori* …

[Phys. Rev. B 95, 014102] Published Fri Jan 06, 2017

]]>The conductivity of $\mathrm{F}{\mathrm{e}}_{3}{\mathrm{O}}_{4}$ drops two orders of magnitude below the Verwey temperature ${T}_{v}$, known as the Verwey transition, due to the formation of charge ordering (CO). Here, we report the discovery of a large birefringence effect correlated with the CO in $\mathrm{F}{\mathrm{e}}_{3}{\mathrm{O}}_{4}$ controlled by ultrafast-laser-assisted …

[Phys. Rev. B 95, 014103] Published Fri Jan 06, 2017

]]>Recent experiments performed in current-driven nanocontacts with strong perpendicular anisotropy have shown that spin-transfer torque can drive self-localized spin waves [W. H. Rippard, A. M. Deac, M. R. Pufall, J. M. Shaw, M. W. Keller, S. E. Russek, G. E. W. Bauer, and C. Serpico, Phys. Rev. B **81**,…

[Phys. Rev. B 95, 024106] Published Fri Jan 06, 2017

]]>With infrared (IR) and terahertz (THz) ellipsometry we investigated the anisotropy of the IR-active phonon modes in ${\text{SrTiO}}_{3}$ (110) single crystals in the tetragonal state below the so-called antiferrodistortive transition at ${T}^{*}=105$ K. In particular, we show that the anisotropy of the oscillator streng…

[Phys. Rev. B 95, 024105] Published Thu Jan 05, 2017

]]>Oxide-embedded bulk iron is investigated in terms of first principles calculations and data mining. Twenty-nine oxides are embedded into a vacancy site of iron where first principles calculations are performed and the resulting calculations are stored as a data set. A prediction of the dissolution e…

[Phys. Rev. B 95, 014101] Published Wed Jan 04, 2017

]]>In ferroelectric materials the maximum electrostrain effect usually occurs at a phase boundary (often referred to as a “morphotropic phase boundary”) between two or more different phases due to lattice instability at such compositions. As a result it is not expected that the electrostrain maximum ca…

[Phys. Rev. B 95, 020101(R)] Published Wed Jan 04, 2017

]]>The atomic-level structures of liquids and glasses are amorphous, lacking long-range order. We characterize the atomic structures by integrating radial distribution functions (RDF) from molecular dynamics (MD) simulations for several metallic liquids and glasses: $\mathrm{C}{\mathrm{u}}_{46}\mathrm{Z}{\mathrm{r}}_{54},\mathrm{N}{\mathrm{i}}_{80}\mathrm{A}{\mathrm{l}}_{20},\mathrm{N}{\mathrm{i}}_{33.3}\mathrm{Z}{\mathrm{r}}_{66.7}$, an…

[Phys. Rev. B 95, 024103] Published Wed Jan 04, 2017

]]>The formation and temperature evolution of polar nanoregions (PNRs) in relaxor ferroelectrics is an intriguing issue that is still under debate. Therefore, we present an approach to estimate the volume fraction of PNRs by the example of the relaxor ferroelectric, $(1-x)\left(\mathrm{B}{\mathrm{i}}_{0.5}\mathrm{N}{\mathrm{a}}_{0.5}\right)\mathrm{Ti}{\mathrm{O}}_{3}-x\mathrm{BaTi}{\mathrm{O}}_{3}$ (BNT-$x\dots $

[Phys. Rev. B 95, 024104] Published Wed Jan 04, 2017

]]>The occurrence of so-called temperature-induced neutral-ionic transitions (TINIT) in mixed-stack charge-transfer crystals is quite rare. Here we reinvestigate one of the crystals which has been claimed to undergo such a transition, $3,{3}^{\prime},5,{5}^{\prime}$-tetramethylbenzidine-tetracyanoquinodimethane (TMB-TCNQ). …

[Phys. Rev. B 95, 024101] Published Tue Jan 03, 2017

]]>Olivine $\mathrm{LiMnP}{\mathrm{O}}_{4}$ is a promising cathode material for Li-ion batteries. One drawback of this material is the propensity of its delithiated phase, $\mathrm{MnP}{\mathrm{O}}_{4}$, to evolve oxygen gas above approximately 200 °C. During thermal runaway of cells, this oxygen gas can burn the electrolyte and other cell components …

[Phys. Rev. B 95, 024102] Published Tue Jan 03, 2017

]]>The damping $\left(\mathrm{\Gamma}a\right)$ of the transverse acoustic (TA) phonon in single crystals of the relaxor $\mathrm{KT}{\mathrm{a}}_{1-x}\mathrm{N}{\mathrm{b}}_{x}{\mathrm{O}}_{3}$ with $x=0.15\u20130.17$ was studied by means of high resolution inelastic cold neutron scattering near the (200) Brillouin Zone (BZ) point where diffuse scattering is absent, although it is present near (1…

[Phys. Rev. B 94, 214116] Published Fri Dec 30, 2016

]]>In the morphotropic phase boundary region where tetragonal and rhombohedral phases coexist in the ferroelectric solid solution ${\mathrm{PbZr}}_{1-x}{\mathrm{Ti}}_{x}{\mathrm{O}}_{3}$(PZT), large strains can be induced at the interface due to the lattice misfit of the two structures. We show that for bulk PZT the misfit strains between tetrag…

[Phys. Rev. B 94, 214117] Published Fri Dec 30, 2016

]]>The *ab initio* electronic structure calculations of the ${\mathrm{Ni}}_{2}\mathrm{MnGa}$ alloy indicate that the orthorhombic 4O structure exhibits the lowest energy compared to all known martensitic structures. The 4O structure is formed by nanotwin double layers, i.e., oppositely oriented nanotwins consisting of two (101) …

[Phys. Rev. B 94, 224108] Published Fri Dec 30, 2016

]]>Ordering and disordering processes in complex oxides strongly influence their physicochemical properties when they are submitted to severe conditions, such as high temperature, high pressure, or irradiation. This paper examines the role played by the local atomic order on the structural stability of…

[Phys. Rev. B 94, 224109] Published Fri Dec 30, 2016

]]>Aluminum oxide hydroxide, AlOOH, is a prototypical hydrous mineral in the geonomy. The study of the high-pressure phase evolution of AlOOH is of fundamental importance in helping to understand the role of hydrous minerals in the water storage and transport in Earth, as in other planets. Here, we hav…

[Phys. Rev. B 94, 224110] Published Fri Dec 30, 2016

]]>The authors propose a new method for realizing mechanical ground-state cooling that could generate quantum entanglement at convenient temperatures (1 K). They consider a diamond beam bending above a magnetic tip (the beam is clamped at one end and free to move at the other). Near the oscillating end, they insert a lattice defect, specifically a silicon-vacancy center. As the beam bends, the defect experiences a varying magnetic field which may flip its spin by absorbing mechanical energy from the low-frequency flexural motion of the beam. At the same time, the center is coupled to high-frequency compression modes, which locally distort the surrounding lattice and lead to a fast relaxation of the center’s electronic states. By stimulating the defect with microwave fields, these two coupling mechanisms can be connected and an energy flow from the bending motion into the high-frequency phonon reservoir is induced. According to predictions made here, the mechanical temperature of the beam – how much it bends – can then be tuned via optimizing these alternating absorption and reemission processes in the same way the temperature of atoms can be controlled with light.

[Phys. Rev. B 94, 214115] Published Thu Dec 29, 2016

]]>The high efficiency of lead organo-metal-halide perovskite solar cells has raised many questions about the role of the methylammonium (MA) molecules in the Pb-I framework. Experiments indicate that the MA molecules are able to “freely” spin around at room temperature even though they carry an intrin…

[Phys. Rev. B 94, 214114] Published Wed Dec 28, 2016

]]>Utilizing thermal changes in solid-state materials strategically offers caloric-based alternatives to replace current vapor-compression technology. To make full use of multiple forms of the entropy and achieve higher efficiency for designs of cooling devices, the multicaloric effect appears as a cut…

[Phys. Rev. B 94, 214113] Published Tue Dec 27, 2016

]]>Free electrons can screen out long-range Coulomb interaction and destroy the polar distortion in some ferroelectric materials, whereas the coexistence of polar distortion and metallicity were found in several non-central-symmetric metals (NCSMs). Therefore, the mechanisms and designing of NCSMs have…

[Phys. Rev. B 94, 224107] Published Tue Dec 27, 2016

]]>Two kinds of phase diagrams can be observed in doped ferroic materials. A glass phase diagram is formed by doping a nontransforming end into a ferroic matrix, while doping a transforming end forms phase diagrams with a phase boundary separating two different ferroic phases. Here we report a phase di…

[Phys. Rev. B 94, 214112] Published Fri Dec 23, 2016

]]>We use a spin-polarized tight-binding model Hamiltonian and the Landauer transport formalism to investigate the electronic transport properties of carbon nanotubes where different types of holes have been drilled through their sidewalls. We focus on zigzag edged defects with different atomic configu…

[Phys. Rev. B 94, 224106] Published Thu Dec 22, 2016

]]>For NiTi-based alloys, the shape memory effect is governed by a transition from a low-temperature martensite phase to a high-temperature austenite phase. Despite considerable experimental and computational work, basic questions regarding the stability of the phases and the martensitic phase transiti…

[Phys. Rev. B 94, 214110] Published Mon Dec 19, 2016

]]>We investigate the photovoltaic (PV) effects in ferroelectrics based on the polar structure in domains and the intrinsic symmetry breaking of ferroelastic domain walls (DWs). A comprehensive analysis for $\mathrm{BiFe}{\mathrm{O}}_{3}$ films with the single-domain and 71° domain structures reveals a major contribution of th…

[Phys. Rev. B 94, 214111] Published Mon Dec 19, 2016

]]>The martensitic start temperature ${M}_{\text{s}}$ is one of the key characteristics of shape memory materials. High-temperature shape memory alloys are a special class of materials where transformation temperatures between the martensite and austenite phase above 373 K are desirable. For the design of new high-t…

[Phys. Rev. B 94, 224104] Published Mon Dec 19, 2016

]]>The role of defects in van der Waals heterostructures made of graphene and hexagonal boron nitride (h-BN) is studied using a combination of *ab initio* and model calculations. Despite the weak van der Waals interaction between layers, defects residing in h-BN, such as carbon impurities and antisite de…

[Phys. Rev. B 94, 224105] Published Mon Dec 19, 2016

]]>We present microscopically resolved, polarized spectroscopy of Raman scattering collected from tetragonal ${\mathrm{SrTiO}}_{3}$. The anisotropic response of first-order Raman peaks within a single tetragonal domain has been measured. From these data, we assign symmetries to the phonons seen in the first-order Rama…

[Phys. Rev. B 94, 214107] Published Fri Dec 16, 2016

]]>The composition-dependent crystal structure, volume, elastic constants, and electronic structure of $\delta \text{\u2212}{\mathrm{Pu}}_{1-x}{M}_{x}$ $\left(M=\text{Ga and Al},0\le x\le 0.1\right)$ alloys are systematically studied by using first-principles EMTO-CPA calculations. It is shown that the fcc and $L{1}_{2}$ structures co-exist in the alloys with $x\le 0.04$ wherea…

[Phys. Rev. B 94, 214108] Published Fri Dec 16, 2016

]]>It is well established that when energetic ions are moving in crystals, they may penetrate much deeper if they happen to be directed in some specific crystal directions. This ‘channeling’ effect is utilized for instance in certain ion beam analysis methods and has been described by analytical theori…

[Phys. Rev. B 94, 214109] Published Fri Dec 16, 2016

]]>In approximate density-functional theory (DFT), the self-interaction error is an electron delocalization anomaly associated with underestimated insulating gaps. It exhibits a predominantly quadratic energy-density curve that is amenable to correction using efficient, constraint-resembling methods su…

[Phys. Rev. B 94, 220104(R)] Published Fri Dec 16, 2016

]]>The time needed for metals to respond structurally to electronic excitation is usually considered to be set by picosecond-long electron-phonon coupling, hence limiting the rapid achievement of structural phase changes. Via time-resolved ellipsometry, we show that fs laser excitation of tungsten dete…

[Phys. Rev. B 94, 224103] Published Fri Dec 16, 2016

]]>The scattering of elastic waves by three-dimensional obstacles in isotropic elastic zero-index-metamaterials (ZIM) is theoretically investigated. We show that the zero values of each single effective parameter and their various combinations of the elastic ZIM can produce different types of wave prop…

[Phys. Rev. B 94, 224102] Published Wed Dec 14, 2016

]]>We comparably performed polarized Raman scattering studies of $\mathrm{MoT}{\mathrm{e}}_{2}$ and $\mathrm{WT}{\mathrm{e}}_{2}$. By rotating crystals to tune the angle between the principal axis of the crystals and the polarization of the incident/scattered light, we obtained the angle dependence of the intensities for all the observed modes, which …

[Phys. Rev. B 94, 214105] Published Tue Dec 13, 2016

]]>Direct mesoscale measurements of radiation-induced changes in the mechanical properties of bulk materials remain difficult to perform. Most widely used characterization techniques are either macro- or microscale in nature, focusing on overall properties or overly small areas for analysis. Linking th…

[Phys. Rev. B 94, 214106] Published Tue Dec 13, 2016

]]>Pressure and shear strain-induced phase transformations (PTs) in a nanograined bicrystal at the evolving dislocations pile-up have been studied utilizing a phase field approach (PFA). The complete system of PFA equations for coupled martensitic PT, dislocation evolution, and mechanics at large strai…

[Phys. Rev. B 94, 214104] Published Thu Dec 08, 2016

]]>We propose a scheme which can generate a highly directional single photon with almost 100% efficiency. Therefore we can get a useful single photon when it is required. An initial excited atom is placed inside a special Fabry-Pérot cavity whose walls consist of left-handed and zero-index metamaterial…

[Phys. Rev. B 94, 220103(R)] Published Thu Dec 08, 2016

]]>We present diffuse x-ray scattering data on the strong negative thermal expansion (NTE) material ${\mathrm{ScF}}_{3}$ and find that two-dimensional nanoscale correlations exist at momentum-space regions associated with possibly rigid rotations of the perovskite octahedra. We address the extent to which rigid octahe…

[Phys. Rev. B 94, 214102] Published Wed Dec 07, 2016

]]>We report a Raman scattering study of six rare-earth orthoferrites $R{\mathrm{FeO}}_{3}$, with $R$ = La, Sm, Eu, Gd, Tb, Dy. The use of extensive polarized Raman scattering of ${\mathrm{SmFeO}}_{3}$ and first-principles calculations enable the assignment of the observed phonon modes to vibrational symmetries and atomic displacements…

[Phys. Rev. B 94, 214103] Published Wed Dec 07, 2016

]]>Recent experiments on ice formed by water under nanoconfinement provide evidence for a two-dimensional (2D) “square ice” phase. However, the interpretation of the experiments has been questioned and the stability of square ice has become a matter of debate. Partially this is because the simulation a…

[Phys. Rev. B 94, 220102(R)] Published Tue Dec 06, 2016

]]>Single crystals of ${\mathrm{PbZrO}}_{3}$ have been studied by dynamic mechanical analysis measurements in the low-frequency range $f=0.02$–50 Hz. The complex Young's modulus exhibits a quite rich behavior and depends strongly on the direction of the applied dynamic force. In pseudocubic ${\left[100\right]}_{c}$ direction, we found in…

[Phys. Rev. B 94, 214101] Published Fri Dec 02, 2016

]]>Phase decomposition is a well-known process leading to the formation of two-phase mixtures. Here we show that a strain imposed on a ferroelastic crystal promotes the formation of mixed phases and domains, i.e., strain phase separation with local strains determined by a common tangent construction on…

[Phys. Rev. B 94, 220101(R)] Published Fri Dec 02, 2016

]]>In the conceptual framework of phase ordering after temperature quenches below transition, we consider the underdamped Bales-Gooding-type “momentum conserving” dynamics of a 2D martensitic structural transition from a square-to-rectangle unit cell. The one-component or ${N}_{\mathrm{OP}}=1$ order parameter is one o…

[Phys. Rev. B 94, 224101] Published Fri Dec 02, 2016

]]>Extensive *ab initio* simulations of ice-water basal interface at seven temperatures in the range 250–400 K were performed in NVT and NPT ensembles with a collection of 389 water molecules in order to estimate the melting point of ice from direct liquid-solid two-phase coexistence. Density functional …

[Phys. Rev. B 94, 184111] Published Tue Nov 29, 2016

]]>We present a comprehensive density-functional theory study of total energy and structural properties of As, Sb, and Bi in their A7 ground-state structure and in the bcc, fcc, and simple cubic (sc) modifications. We also investigate continuous structural transitions between these structures. The elec…

[Phys. Rev. B 94, 184110] Published Mon Nov 28, 2016

]]>Structural stability, electronic structure, and optical properties of ${\mathrm{CH}}_{3}{\mathrm{NH}}_{3}{\mathrm{BaI}}_{3}$ hybrid perovskite are examined from theory as well as experiment. Solution-processed thin films of ${\mathrm{CH}}_{3}{\mathrm{NH}}_{3}{\mathrm{BaI}}_{3}$ exhibited a high transparency in the wavelength range of 400–825 nm (1.5–3.1 eV for which the photon current …

[Phys. Rev. B 94, 180105(R)] Published Wed Nov 23, 2016

]]>The formalism to construct the machine learning potentials (MLPs) is presented. We introduce the spilling factor for the simultaneous error estimation and the recursive bisection method for the reduction of the computational cost. The formalism is applied for the $\beta $-phase vanadium monohydride. The fi…

[Phys. Rev. B 94, 184109] Published Wed Nov 23, 2016

]]>Ferroelectric materials encode information through the displacement of atoms within the unit cell, but the ultimate speed limits governing how fast the polarization can change and how it responds to electric fields remain largely unknown. These processes in turn fundamentally determine the functionality of ferroelectric materials within devices. Here, the authors show that single-cycle light pulses at terahertz frequencies can be used as an ultrafast electric field to drive large amplitude rotations of the ferroelectric polarization on picosecond time scales within the prototypical ferroelectric BaTiO${}_{3}$, probed by femtosecond x-ray scattering to directly resolve the motions of the atoms. These measurements are connected directly to first-principles molecular dynamics simulations of ultrafast electric-field-driven effects in ferroelectrics with good agreement obtained between experiment and theory.

[Phys. Rev. B 94, 180104(R)] Published Tue Nov 22, 2016

]]>Using the Landau-Ginzburg-Devonshire theory, we established the role of the flexoelectric coupling between the gradients of elastic strain and polarization in the stability of spatially modulated phases in ferroics, such as incipient and proper ferroelectrics with commensurate and incommensurate lon…

[Phys. Rev. B 94, 174112] Published Mon Nov 21, 2016

]]>Both ${180}^{\circ}$ and ${90}^{\circ}$ intrinsic polarization switching (IPS) in $\mathrm{BaTi}{\mathrm{O}}_{3}$ crystal were investigated by Landau-Ginzburg-Devonshire (LGD) theory under combined electric field and stress loading. Results show that for ${180}^{\circ}\phantom{\rule{0.16em}{0ex}}\mathrm{PS}$, the coercive electric field $\left({E}_{IC}^{{180}^{\circ}}\right)$ increases under tension but decreases under co…

[Phys. Rev. B 94, 184108] Published Mon Nov 21, 2016

]]>First-principles methods are employed to determine the structural, mechanical, and thermodynamic reasons for the experimentally reported cubic WN phase. The defect-free rocksalt phase is both mechanically and thermodynamically unstable, with a negative single crystal shear modulus ${C}_{44}=\phantom{\rule{0.16em}{0ex}}-86\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ and a p…

[Phys. Rev. B 94, 174111] Published Fri Nov 18, 2016

]]>Motivated by the resurgence of electronic and optical property design in ordered fluoride and oxyfluoride compounds, we present a density functional theory (DFT) study of 19 materials with structures, ranging from simple to complex, and variable oxygen-to-fluorine ratios. We focus on understanding t…

[Phys. Rev. B 94, 174108] Published Wed Nov 16, 2016

]]>The $\mathrm{Xe}\text{\u2212}{\mathrm{N}}_{2}$ binary phase diagram was determined at 296 K from the pressure evolution of 14 different concentrations. The properties of $\mathrm{Xe}\text{\u2212}{\mathrm{N}}_{2}$ mixtures were characterized using visual observation, Raman spectroscopy, and powder x-ray diffraction. Above 4.9 GPa, the $\mathrm{Xe}({\mathrm{N}}_{2}{)}_{2}$ van der Waals compound is stab…

[Phys. Rev. B 94, 174109] Published Wed Nov 16, 2016

]]>We study the temperature dependence of the charge density wave (CDW) in a chromium thin film using x-ray diffraction. We exploit the interference between the CDW satellite peaks and Laue oscillations to determine the amplitude, the phase, and the period of the CDW. We find discrete half-integer peri…

[Phys. Rev. B 94, 174110] Published Wed Nov 16, 2016

]]>A equation of state (EOS) experimental technique that enables the study of thermodynamic derivatives into the TPa regime is described and applied to boron carbide (${\mathrm{B}}_{4}\mathrm{C}$). Data presented here are principal Hugoniot sound speed measurements reported using a laser-driven shock platform, providing a mean…

[Phys. Rev. B 94, 184107] Published Wed Nov 16, 2016

]]>We report a study of the strain state of epitaxial MnSi films on Si(111) substrates in the thick film limit (100–500 Å) as a function of film thickness using polarization-dependent extended x-ray absorption fine structure (EXAFS). All films investigated are phase-pure and of high quality with a shar…

[Phys. Rev. B 94, 174107] Published Tue Nov 15, 2016

]]>We have conducted high-pressure x-ray diffraction and Raman spectroscopic studies on the $\mathrm{CdC}{\mathrm{r}}_{2}\mathrm{S}{\mathrm{e}}_{4}$ spinel at room temperature up to 42 GPa. We have resolved three structural transitions up to 42 GPa, i.e., the starting $Fd\overline{3}m$ phase transforms at $\sim 11\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ into a tetragonal $I{4}_{1}/amd$ structure, an orthorhom…

[Phys. Rev. B 94, 174106] Published Mon Nov 14, 2016

]]>We report on transmission electron microscope beam-induced ferroelectric domain nucleation and motion. While previous observations of this phenomenon have been reported, a consistent theory explaining induced domain response is lacking, and little control over domain behavior has been demonstrated. …

[Phys. Rev. B 94, 174104] Published Fri Nov 11, 2016

]]>We analyze theoretically the finite-temperature polarization dynamic in displacive-type ferroelectrics. In particular we consider the thermally activated switching time of a single-domain ferroelectric polarization studied by means of the Landau-Khalatnikov equation, extended to capture thermal fluc…

[Phys. Rev. B 94, 174105] Published Fri Nov 11, 2016

]]>This paper reports on symmetry breaking in the aperiodic inclusion compound $n\text{-octadecane/urea}$ and its isotopomer $n\text{-octadecane/urea-}{d}_{4}$. The high-symmetry phase is described by a hexagonal rank-4 superspace group. Pretransitional phenomena in this crystallographic superspace reveal competing short-ran…

[Phys. Rev. B 94, 184105] Published Fri Nov 11, 2016

]]>We investigated the crystal structures and dielectric properties of an improper ferroelectric ${\mathrm{Ba}}_{1-x}{\mathrm{Sr}}_{x}{\mathrm{Al}}_{2}{\mathrm{O}}_{4}(x\le 0.1)$ and revealed that suppressing the condensation of the $M$-point soft mode involves the emergence of a “fluctuating” state. In the low-Sr-concentration region of $x\le 0.06$, crystals exhibit …

[Phys. Rev. B 94, 184106] Published Fri Nov 11, 2016

]]>We have examined the effects of field cooling on the phase diagram of the relaxor system $(1-x)\mathrm{Pb}\left(\mathrm{Z}{\mathrm{n}}_{1/3}\mathrm{N}{\mathrm{b}}_{2/3}\right){\mathrm{O}}_{3}-x\mathrm{PbTi}{\mathrm{O}}_{3}$ (PZN-$x\mathrm{PT}$) for compositions near the morphotropic phase boundary (MPB). High-resolution diffraction measurements using Cu ${K}_{\alpha}$ x rays, which probe $\approx 3\phantom{\rule{0.16em}{0ex}}\mu \mathrm{m}$ below the crystal surface, were …

[Phys. Rev. B 94, 174103] Published Thu Nov 10, 2016

]]>Magnetic skyrmions are candidates for a new generation of information carriers due to their nanometric size and topologically protected stability. The study of the dynamics of such skyrmions in racetrack geometries and, in general, in confined geometries becomes essential to achieve these goals. Her…

[Phys. Rev. B 94, 184104] Published Thu Nov 10, 2016

]]>Entropy is a critical, but often overlooked, factor in determining the relative stabilities of crystal phases. The importance of entropy is most pronounced in softer materials, where small changes in free energy can drive phase transitions, which has recently been demonstrated in the case of organic…

[Phys. Rev. B 94, 180103(R)] Published Mon Nov 07, 2016

]]>Ferroelectric polymorphic phase coexistence, associated with either the presence of a morphotropic phase boundary or a temperature-driven polymorphic phase transition, is currently acknowledged as the key to high piezoelectric activity and is searched when new perovskite materials are developed, lik…

[Phys. Rev. B 94, 184101] Published Mon Nov 07, 2016

]]>Heusler compounds offer potential as spintronic devices due to their spin polarization and half-metallicity properties, where electron spin-majority (minority) manifold exhibits states (band gap) at the electronic chemical potential, yielding full spin polarization in a single manifold. Yet, Heusler…

[Phys. Rev. B 94, 184102] Published Mon Nov 07, 2016

]]>We consider a film of a normal-state Fermi liquid on a planar substrate. Landau's Fermi liquid theory is applied to calculate the linear response of the film to transverse oscillation of the substrate. The response consists of a collective transverse zero-sound mode, as well as incoherent quasiparti…

[Phys. Rev. B 94, 184103] Published Mon Nov 07, 2016

]]>The effect of atomic *short-range* order on the macroscopic and microscopic properties of the prototype of relaxor ferroelectrics, that is, lead magnesium niobate $\mathrm{Pb}\left({\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}\right){\mathrm{O}}_{3}$ (PMN), is studied via the combination of an annealing technique and a large-scale effective Hamiltonian method. The invest…

[Phys. Rev. B 94, 180102(R)] Published Thu Nov 03, 2016

]]>We explore the role of flexoelectric effect in functional properties of nanoscale ferroelectric films with mixed electronic-ionic conductivity. Using a coupled Ginzburg-Landau model, we calculate spontaneous polarization, effective piezoresponse, elastic strain and compliance, carrier concentration,…

[Phys. Rev. B 94, 174101] Published Wed Nov 02, 2016

]]>The design and synthesis of three-dimensional denser carbons are one of the hot issues in condensed matter physics because of their fascinating properties. Here we identify by *ab initio* calculations several tetragonal and monoclinic polymorphs of carbon that adopt the $t32,t{32}^{*},m32$, and $m{32}^{*}$ struct…

[Phys. Rev. B 94, 174102] Published Wed Nov 02, 2016

]]>The band structure of TaAs provides the necessary conditions for the emergence of Weyl fermions. Measurements verifying this fact are remarkably robust, given the reported levels of nonstoichiometry in typical single crystals. Here we demonstrate the surprising fact that a small degree of nonstoichi…

[Phys. Rev. B 94, 180101(R)] Published Tue Nov 01, 2016

]]>The pressure-induced phase transition of monazite-type ${\mathrm{LaPO}}_{4}$ at $\approx 26$ GPa is studied by single-crystal x-ray diffraction and second harmonic generation (SHG) up to 31 GPa. The structure of the postmonazite phase of ${\mathrm{LaPO}}_{4}$ has been obtained and it is shown that it corresponds to a post-barite-type struc…

[Phys. Rev. B 94, 134109] Published Fri Oct 28, 2016

]]>To investigate the barrier effect of grain boundaries on the propagation of avalanchelike plasticity at the atomic scale, we perform three-dimensional molecular dynamics simulations by using simplified polycrystal models including symmetric-tilt grain boundaries. The cutoffs of the stress-drop distr…

[Phys. Rev. B 94, 140102(R)] Published Tue Oct 25, 2016

]]>In addition to the single polarization-versus-electric field hysteresis loop that is characteristic of ferroelectrics and the double hysteresis loop that is known to occur in antiferroelectrics, a third kind of polarization-versus-electric field function has been reported in several systems. This th…

[Phys. Rev. B 94, 140101(R)] Published Mon Oct 24, 2016

]]>We investigate analytically and numerically the interaction between grain boundaries and second phase precipitates in two-phase coherent solids in the presence of misfit strain. Our numerical study uses amplitude equations that describe the interaction of composition and stress [R. Spatschek and A. …

[Phys. Rev. B 94, 144106] Published Mon Oct 24, 2016

]]>The long-time thermal relaxation of (TMTTF)${}_{2}\mathrm{Br},{\mathrm{Sr}}_{14}{\mathrm{Cu}}_{24}{\mathrm{O}}_{41}$ and ${\mathrm{Sr}}_{2}{\mathrm{Ca}}_{12}{\mathrm{Cu}}_{24}{\mathrm{O}}_{41}$ single crystals at temperatures below 1 K and magnetic field up to 10 T is investigated. The data allow us to determine the relaxation-time spectrum of the low-energy excitations caused by the charge-density wave or spin-d…

[Phys. Rev. B 94, 144107] Published Mon Oct 24, 2016

]]>The strength of a material can be altered by temperature, pressure, grain size, and orientation distributions. At the microscale, neighboring grains often play important roles in the elastic and plastic deformation process. By applying high pressure to a mixture of germanium and gold powder in the v…

[Phys. Rev. B 94, 144104] Published Fri Oct 21, 2016

]]>We present *ab initio* results for linker decorations in Mg-MOF74, i.e., attaching various metals $\mathcal{M}=\text{Li}$, Na, K, Sc, Cr, Mn, Fe, Ni, Cu, Zn, Rb, Pd, Ag, and Pt near the ring of the linker, creating new strong adsorption sites and thus maximizing small-molecule uptake. We find that in most cases these de…

[Phys. Rev. B 94, 144105] Published Fri Oct 21, 2016

]]>We report a high-pressure study of monoclinic monazite-type $\mathrm{SrCr}{\mathrm{O}}_{4}$ up to 26 GPa. Therein we combined x-ray diffraction, Raman, and optical-absorption measurements with *ab initio* calculations, to find a pressure-induced structural phase transition of $\mathrm{SrCr}{\mathrm{O}}_{4}$ near 8–9 GPa. Evidence of a second phase tr…

[Phys. Rev. B 94, 134108] Published Thu Oct 20, 2016

]]>We study the dynamics of quantum three-level systems due to fast fluctuations of their environment (white noise). As an example, we model the decoherence and dephasing of nitrogen-vacancy (NV) centers in diamond that are positioned near a surface that gives rise to quickly fluctuating magnetic field…

[Phys. Rev. B 94, 134107] Published Wed Oct 19, 2016

]]>A system driven in the vicinity of its critical point by varying a relevant field in an arbitrary function of time is a generic system that possesses a long relaxation time compared with the driving time scale and thus represents a large class of nonequilibrium systems. For such a manifestly nonline…

[Phys. Rev. B 94, 144103] Published Wed Oct 19, 2016

]]>We investigate phase separation including elastic coherency effects in the bulk and at surfaces and find a reduction of the solubility limit in the presence of free surfaces. This mechanism favors phase separation near free surfaces even in the absence of external stresses. We apply the theory to hy…

[Phys. Rev. B 94, 134106] Published Tue Oct 18, 2016

]]>Three extensive density functional/molecular dynamics simulations of the crystallization of amorphous ${\mathrm{Ge}}_{2}{\mathrm{Sb}}_{2}{\mathrm{Te}}_{5}$ (460 atoms) [Phys. Rev. B **90**, 184109 (2014)] have been completed with simulation times of up to 8.2 ns. Together with the results of earlier simulations with and without a crystallite seed…

[Phys. Rev. B 94, 134105] Published Mon Oct 17, 2016

]]>Thorium and its compounds have received considerable attention in recent years due to the renewed interest in developing the thorium fuel cycle as an alternative nuclear energy technology. There is pressing current need to explore the physical properties essential to the fundamental understanding an…

[Phys. Rev. B 94, 134104] Published Fri Oct 07, 2016

]]>Precipitation of anion nanocrystals (NCs) in initially stoichiometric II-VI crystals under hydrostatic pressure and light exposure is explored by Raman spectroscopy, and the mechanism for this effect is analyzed by model calculations. ZnSe, ZnTe, and CdSe crystals are studied in bulk and/or epitaxia…

[Phys. Rev. B 94, 134102] Published Thu Oct 06, 2016

]]>Strongly scattering elastic media, such as consolidated granular materials, respond to ultrasonic pulse excitations with a long response signal with peculiar properties. The portion of the signal at late times, termed coda, is due to multiple scattering. It contains information about the elastic pro…

[Phys. Rev. B 94, 134103] Published Tue Oct 04, 2016

]]>A hexagonal structure of solid molecular hydrogen with $P{6}_{1}22$ symmetry is calculated to be more stable below about 200 GPa than the monoclinic $C2/c$ structure identified previously as the best candidate for phase III. We find that the effects of nuclear quantum and thermal vibrations play a central ro…

[Phys. Rev. B 94, 134101] Published Mon Oct 03, 2016

]]>We have performed density functional theory (DFT) based calculations for aluminum in extreme conditions of both pressure and temperature, up to five times compressed ambient density, and over 1 000 000 K in temperature. In order to cover such a domain, DFT methods including phonon calculations, quan…

[Phys. Rev. B 94, 144101] Published Mon Oct 03, 2016

]]>A salient feature of cyclically driven first-order phase transformations in crystals is their scale-free avalanche dynamics. This behavior has been linked to the presence of a classical critical point but the mechanism leading to criticality without extrinsic tuning remains unexplained. Here we show…

[Phys. Rev. B 94, 144102] Published Mon Oct 03, 2016

]]>In electromagnetism, acoustics, and quantum mechanics, scattering problems can routinely be solved numerically by virtue of perfectly matched layers (PMLs) at simulation domain boundaries. Unfortunately, the same has not been possible for general elastodynamic wave problems in continuum mechanics. I…

[Phys. Rev. B 94, 100105(R)] Published Fri Sep 30, 2016

]]>The influence of defect dipoles on the electrocaloric effect (ECE) in acceptor doped ${\mathrm{BaTiO}}_{3}$ is studied by means of lattice-based Monte-Carlo simulations using a Ginzburg-Landau type effective Hamiltonian. Oxygen vacancy-acceptor associates are described by fixed local dipoles with orientation parall…

[Phys. Rev. B 94, 094113] Published Thu Sep 29, 2016

]]>Reversible polymorphism of monolayer transition-metal dichalcogenides (TMDC) has currently attracted much attention from both academic and applied perspectives. Of special interest is ${\mathrm{MoTe}}_{2}$, where the stable semiconducting $2H$ and metastable (semi)metallic $1{T}^{\prime}$ phases have a rather small energy differ…

[Phys. Rev. B 94, 094114] Published Thu Sep 29, 2016

]]>An improved thermodynamic cycle is validated in ferroelectric single crystals, where the cooling effect of an electrocaloric refrigerant is enhanced by applying a reversed electric field. In contrast to the conventional adiabatic heating or cooling by on-off cycles of the external electric field, ap…

[Phys. Rev. B 94, 100104(R)] Published Thu Sep 29, 2016

]]>The general method for the calculation of $n\mathrm{th}$ ($n\ge 2$) order elastic constants of the loaded crystal is given in the framework of the nonlinear elasticity theory. For the crystals of cubic symmetry under hydrostatic compression, the two schemes of calculation of the elastic constants of second, third, …

[Phys. Rev. B 94, 104114] Published Thu Sep 29, 2016

]]>The phase diagram of iridium is investigated using the Z methodology. The Z methodology is a technique for phase diagram studies that combines the direct Z method for the computation of melting curves and the inverse Z method for the calculation of solid-solid phase boundaries. In the direct Z metho…

[Phys. Rev. B 94, 094112] Published Wed Sep 28, 2016

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