As the grain size decreases to the nanometer range, the characteristics of the ferroelectric nanoceramic can be ultimately determined by the competition between two effects: the intrinsic effect that is associated with the local properties of the grain boundary and the extrinsic effect that arises f…

[Phys. Rev. B 95, 054121] Published Fri Feb 24, 2017

]]>The authors present a method for characterizing the hyperuniformity (the suppression of density fluctuations at long wavelengths) for quasicrystals (and other structures whose diffraction pattern includes a dense set of Bragg peaks) based on determining the behavior of the integrated spectral intensity $Z$($k$) for small wavenumber $k$. Surprisingly, we find that quasicrystals with peaks at the same wavenumbers $k$ can have different behavior for $Z$($k$) and, hence, qualitatively different degrees of hyperuniformity. This effect has never been explored in the laboratory. The figure shows a one-dimensional example: two “sidewalks” with different widths (pitched at an incommensurate angle) built on a lawn with a square crystal pattern of spots. The construction rule is that, every time the sidewalk crosses a spot, the sidewalk slab is cut and a new one begins. This rule guarantees both sidewalks are quasicrystalline. But the upper one (a Fibonacci sidewalk) has a different degree of hyperuniformity than the lower one.

[Phys. Rev. B 95, 054119] Published Thu Feb 23, 2017

]]>The role of hydrogen in the photoluminescence (PL) of ZnO was investigated using four different types of bulk ZnO single crystal, with varying concentrations of unintentional hydrogen donor and Group I acceptor impurities. Photoluminescence spectra were measured at 3 K, with emission energies determ…

[Phys. Rev. B 95, 054120] Published Thu Feb 23, 2017

]]>Dielectric and mechanical spectroscopies have been used to investigate ferroelectric transitions and twin wall dynamics in the lead-free ceramic $0.5\mathrm{Ba}\left(\mathrm{Z}{\mathrm{r}}_{0.2}\mathrm{T}{\mathrm{i}}_{0.8}\right){\mathrm{O}}_{3}-0.5\left(\mathrm{B}{\mathrm{a}}_{0.7}\mathrm{C}{\mathrm{a}}_{0.3}\right)\mathrm{Ti}{\mathrm{O}}_{3}$ (abbreviated as BZT-50BCT), which is known to have a high piezoelectric coefficient (${d}_{33}>545\phantom{\rule{0.16em}{0ex}}\mathrm{pC}/\mathrm{N}$). Results from …

[Phys. Rev. B 95, 054116] Published Tue Feb 21, 2017

]]>Applying time-varying magnetic fields to Weyl metals, a pair of Weyl points becomes oscillating. This oscillating monopole and antimonopole pair gives rise to ac Berry magnetic fields, responsible for the emergence of Berry electric fields, which have not been discussed before at least in the contex…

[Phys. Rev. B 95, 054117] Published Tue Feb 21, 2017

]]>We investigate the high-pressure behavior of beryllium, magnesium, and calcium difluorides using *ab initio* random structure searching and density functional theory (DFT) calculations, over the pressure range $0\u201370$ GPa. Beryllium fluoride exhibits extensive polymorphism at low pressures, and we find t…

[Phys. Rev. B 95, 054118] Published Tue Feb 21, 2017

]]>The structural and electronic response of $\mathrm{LaAl}{\mathrm{O}}_{3}$ to biaxial strain in the (111) plane is studied by density functional theory (DFT) and compared with strain in the (001) plane and isostatic strain. For (111) strain, in-plane rotations are stabilized by compressive strain and out-of-plane rotations b…

[Phys. Rev. B 95, 064109] Published Tue Feb 21, 2017

]]>The density matrix renormalization group (DMRG) is one of the most powerful numerical methods available for many-body systems. It has been applied to solve many physical problems, including the calculation of ground states and dynamical properties. In this work, we develop a perturbation theory of t…

[Phys. Rev. B 95, 064110] Published Tue Feb 21, 2017

]]>The phase diagram of uranium has been explored up to 100 GPa and 2000 K by means of *ab initio* molecular dynamics (AIMD) simulations. The lattice dynamics and energetics of the stable phases observed experimentally in this range of pressure and temperature are studied in this work. The phonon spectra…

[Phys. Rev. B 95, 054113] Published Fri Feb 17, 2017

]]>Phase-change memories are usually associated with GeTe-${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ quasibinary alloys, where the large optical contrast between the crystalline and amorphous phases is attributed to the formation of resonant bonds in the crystalline phase, which has a rocksalt-like structure. The recent findings that tet…

[Phys. Rev. B 95, 054114] Published Fri Feb 17, 2017

]]>The structural and magnetic properties of multiferroic CuO have been studied by means of neutron and x-ray powder diffraction at pressures up to 11 and 38 GPa, respectively, and by first-principles theoretical calculations. Anomalous lattice compression is observed, with enlargement of the lattice p…

[Phys. Rev. B 95, 054115] Published Fri Feb 17, 2017

]]>Element boron tends to form an icosahedral motif involving 26 electrons, leading to intriguing bonding conditions which complicate understating the structural variations under high pressure. Here we used density function theory (DFT) to examine the mechanical response of β- and recent discovered τ-b…

[Phys. Rev. B 95, 064108] Published Fri Feb 17, 2017

]]>A robust molecular-dynamics simulation method for calculating dislocation core energies has been developed. This method has unique advantages: It does not require artificial boundary conditions, is applicable for mixed dislocations, and can yield converged results regardless of the atomistic system …

[Phys. Rev. B 95, 054112] Published Thu Feb 16, 2017

]]>At high pressure, Mg is expected to transform to the body-centered-cubic (BCC) phase. We use density functional theory to explore the structure of $\langle 111\rangle $-type dislocation cores in BCC Mg as a function of pressure. As the pressure is reduced from the region of absolute stability for the BCC phase, the…

[Phys. Rev. B 95, 064107] Published Thu Feb 16, 2017

]]>While first-principles density functional theory (DFT)-based models have been effective in capturing the physics of ferroelectric phase transitions in ${\mathrm{BaTiO}}_{3},{\mathrm{PbTiO}}_{3}$, and ${\mathrm{KNbO}}_{3}$, quantitative estimates of the transition temperatures (${T}_{C}$) suffer from errors that are believed to originate from the erro…

[Phys. Rev. B 95, 054111] Published Wed Feb 15, 2017

]]>The report on square ice sandwiched between two graphene layers by Algara-Siller *et al.* [Nature (London) **519**, 443 (2015)] has generated a large interest in this system. By applying high lateral pressure on nanoconfined water, we found that monolayer ice is transformed to bilayer ice when the two gra…

[Phys. Rev. B 95, 064105] Published Wed Feb 15, 2017

]]>The capillary forces in mesoporous materials, when imbibed with liquid, are large enough to induce mechanical deformations. Using anisotropic porous silicon, we show that systematic measurements of strain as a function of the pore pressure can yield most of the elastic constants characterizing the p…

[Phys. Rev. B 95, 064106] Published Wed Feb 15, 2017

]]>Descriptors for the bulk modulus of amorphous carbon are investigated through the implementation of data mining where data sets are prepared using first-principles calculations. Data mining reveals that the number of bonds in each C atom and the density of amorphous carbon are found to be descriptor…

[Phys. Rev. B 95, 054110] Published Tue Feb 14, 2017

]]>The change of the lattice dynamics upon the charge disproportionation (CD) transition has been investigated for the ${\mathrm{CaFeO}}_{3}$ crystal by measuring its infrared optical spectra. Across the CD transition, ${\mathrm{CaFeO}}_{3}$ undergoes a metal-insulator transition, and it is found that below ${T}_{CD}\approx 290$ K the low-frequenc…

[Phys. Rev. B 95, 064104] Published Tue Feb 14, 2017

]]>Acoustic metamaterials have exhibited extraordinary potential for manipulating the propagation of sound waves. To date, it has been a challenge to control the propagation of a sound wave through arbitrary pathways in a network. Here, we design a symmetry-breaking, cross-shaped metamaterial comprisin…

[Phys. Rev. B 95, 054109] Published Fri Feb 10, 2017

]]>Plastic deformation of crystalline and amorphous matter often involves intermittent local strain burst events. To understand the physical background of the phenomenon a minimal stochastic mesoscopic model was introduced, where details of the microstructure evolution are statistically represented in …

[Phys. Rev. B 95, 054108] Published Thu Feb 09, 2017

]]>Through three-dimensional discrete dislocation dynamics simulations, we show that by tuning the mode of external loading, the collective dynamics of dislocations undergo a transition from driven avalanches under stress control to quasiperiodic oscillations under strain control. We directly correlate…

[Phys. Rev. B 95, 064103] Published Wed Feb 08, 2017

]]>Three Mo-based transition-metal dichalcogenides ${\mathrm{MoS}}_{2},{\mathrm{MoSe}}_{2}$, and ${\mathrm{MoTe}}_{2}$ share at ambient conditions the same structure $2{H}_{c}$, consisting of layers where Mo atoms are surrounded by six chalcogen atoms in trigonal prism coordination. The knowledge of their high-pressure behavior is, however, limited, part…

[Phys. Rev. B 95, 054105] Published Tue Feb 07, 2017

]]>We build a theoretical model for the electronic properties of the two-dimensional (2D) electron gas that forms at the interface between insulating ${\mathrm{SrTiO}}_{3}$ and a number of polar cap layers, including ${\mathrm{LaTiO}}_{3}$, ${\mathrm{LaAlO}}_{3}$, and ${\mathrm{GdTiO}}_{3}$. The model treats conduction electrons within a tight-binding approximation…

[Phys. Rev. B 95, 054106] Published Tue Feb 07, 2017

]]>We study a model ${\mathrm{SrTiO}}_{3}$ interface in which conduction ${t}_{2g}$ electrons couple to the ferroelectric (FE) phonon mode. We treat the FE mode within a self-consistent phonon theory that captures its quantum critical behavior and show that proximity to the quantum critical point leads to universal tails in …

[Phys. Rev. B 95, 054107] Published Tue Feb 07, 2017

]]>Density-functional calculations of lattice dynamics and high-resolution synchrotron powder diffraction uncover antiferroelectric distortion in the kagome francisite ${\mathrm{Cu}}_{3}\mathrm{Bi}{\left({\mathrm{SeO}}_{3}\right)}_{2}{\mathrm{O}}_{2}\mathrm{Cl}$ below 115 K. Its Br-containing analog is stable in the room-temperature crystal structure down to at least 10 K, altho…

[Phys. Rev. B 95, 064102] Published Tue Feb 07, 2017

]]>In this article, we report negative thermal expansion and spin frustration in hexagonal ${\mathrm{GdInO}}_{3}$. Rietveld refinements of the x-ray diffraction patterns reveal that the negative thermal expansion in the temperature range of 50–100 K stems from the triangular lattice of ${\mathrm{Gd}}^{3+}$ ions. The downward deviatio…

[Phys. Rev. B 95, 054103] Published Mon Feb 06, 2017

]]>Oxygen vacancy-vacancy interactions in rutile $\mathrm{Ti}{\mathrm{O}}_{2}$ are studied in conjunction with polaron formation trends using density functional theory calculations. It is found that polarons strongly enhance the formation of oxygen vacancies in this material and also mediate the interactions between existing v…

[Phys. Rev. B 95, 054104] Published Mon Feb 06, 2017

]]>Boron carbide exhibits intrinsic substitutional disorder over a broad composition range. The structure consists of 12-atom icosahedra placed at the vertices of a rhombohedral lattice, together with a 3-atom chain along the threefold axis. In the high-carbon limit, one or two carbon atoms can replace…

[Phys. Rev. B 95, 054101] Published Fri Feb 03, 2017

]]>The melting curve of Sn initially rises steeply as a function of pressure but exhibits a decrease in slope ($d{T}_{m}/dP$) above 40 GPa to become nearly flat above 50 GPa. Previous studies have argued that a body-centered tetragonal (bct) to cubic (bcc) phase transition occurs in this range at room tempera…

[Phys. Rev. B 95, 054102] Published Fri Feb 03, 2017

]]>The phase diagram of numerous materials of technological importance features high-symmetry high-temperature phases that exhibit phonon instabilities. Leading examples include shape-memory alloys, as well as ferroelectric, refractory, and structural materials. The thermodynamics of these phases have …

[Phys. Rev. B 95, 064101] Published Thu Feb 02, 2017

]]>Various out-of-equilibrium processes produce a supersaturation of vacancies in the material. When these defects show attractive binding energy with solutes, they will form stable point defect-solute clusters which will stabilize solutes in the solid solution with respect to the equilibrium case. Hen…

[Phys. Rev. B 95, 014113] Published Mon Jan 30, 2017

]]>Recent application of neural networks (NNs) to modeling interatomic interactions has shown the learning machines' encouragingly accurate performance for select elemental and multicomponent systems. In this study we explore the possibility of building a library of NN-based models by introducing a hie…

[Phys. Rev. B 95, 014114] Published Mon Jan 30, 2017

]]>$\mathrm{SrCo}{\mathrm{O}}_{2.5}$ has a long-range oxygen vacancy ordering that makes it a promising energy material and catalyst carrier. The study of its electronic properties is vital for its practical applications. Here, we investigate its electronic behavior and lattice structural evolution under high pressure up to 22…

[Phys. Rev. B 95, 024115] Published Mon Jan 30, 2017

]]>To understand how the constituent atoms participate in the hydrogenation of Pd-based alloys at $\sim 0.1$ MPa of hydrogen pressure $\left({P}_{{\mathrm{H}}_{2}}\right)$, we investigated the electronic states in Pd-$M$ $(M=\text{Ru},\text{Rh},\text{Ag},\text{and Au})$ alloys and their hydrides element-selectively by using x-ray absorption spectroscopy at the ${L}_{2,3}$ edges…

[Phys. Rev. B 95, 024116] Published Mon Jan 30, 2017

]]>We establish some general dynamical properties of quantum many-body systems that are subject to a high-frequency periodic driving. We prove that such systems have a quasiconserved extensive quantity ${H}_{*}$, which plays the role of an effective static Hamiltonian. The dynamics of the system (e.g., evolut…

[Phys. Rev. B 95, 014112] Published Fri Jan 27, 2017

]]>The domain structure of hexagonal manganites is simulated based on the phenomenological Ginzburg-Landau theory, and special attention is paid to the evolution of a topological vortex-antivortex pattern with the varying out-of-plane anisotropies of two stiffness parameters for the in-plane ($xy$-plane)…

[Phys. Rev. B 95, 024114] Published Fri Jan 27, 2017

]]>Using first-principles calculations we examine the crystal structures and phase transitions of nitride perovskite ${\mathrm{LaWN}}_{3}$. Lattice dynamics calculations indicate that the ground-state structure belongs to space group $R3c$. Two competitive phase transition pathways are identified which are characterized…

[Phys. Rev. B 95, 014111] Published Thu Jan 26, 2017

]]>The nickel-carbon system has received increased attention over the past years due to the relevance of nickel as a catalyst for carbon nanotube and graphene growth, where nickel carbide intermediates may be involved or carbide interface layers form in the end. Nickel-carbon composite thin films compr…

[Phys. Rev. B 95, 024113] Published Thu Jan 26, 2017

]]>Using density functional theory (DFT) and density functional perturbation theory (DFPT), we investigate the stability and response functions of ${\mathrm{CsH}}_{2}{\mathrm{PO}}_{4}$, a ferroelectric material at low temperature. This material cannot be described properly by the usual (semi)local approximations within DFT. The lon…

[Phys. Rev. B 95, 024112] Published Wed Jan 25, 2017

]]>This work investigates the high-pressure structure of $\mathrm{C}{\mathrm{s}}_{2}\mathrm{CoC}{\mathrm{l}}_{4}$ and how it affects the electronic and vibrational properties using optical absorption, Raman spectroscopy, x-ray diffraction, and x-ray absorption in the 0–15 GPa range. In particular, we focus on the electronic and local structures of $\mathrm{C}{\mathrm{\dots}}^{}$

[Phys. Rev. B 95, 014110] Published Tue Jan 24, 2017

]]>An extensive study of hydroxyl salts $\mathrm{C}{\mathrm{o}}_{2}{\left(\mathrm{OD}\right)}_{3}\mathrm{Cl}/\mathrm{C}{\mathrm{o}}_{2}{\left(\mathrm{OH}\right)}_{3}\mathrm{Cl}$ utilizing muon-spin-relaxation (*μ*SR), nuclear magnetic resonance (NMR), and Raman spectroscopy, supplemented by dielectric constant and magnetic susceptibility measurements, has revealed a unique multiferroic system with deuterium-order-type…

[Phys. Rev. B 95, 024111] Published Tue Jan 24, 2017

]]>The thermal noise in amorphous oxides is the limiting factor for gravitational wave detectors and other high-precision optical devices. Through the fluctuation-dissipation theorem, the thermal noise is directly connected to the internal friction (${Q}^{-1}$). Computational calculations of ${Q}^{-1}$ that use a tw…

[Phys. Rev. B 95, 014109] Published Mon Jan 23, 2017

]]>The ${\mathrm{H}}_{3}\mathrm{S}$ compound was reproducibly synthesized by laser heating hydrogen-embedded solid sulfur samples at various pressures above 75 GPa in a diamond anvil cell. X-ray diffraction studies were conducted up to 160 GPa and the crystal structure has been identified with space group $Cccm$. The stability o…

[Phys. Rev. B 95, 020104(R)] Published Mon Jan 23, 2017

]]>Mainly ruled by oxygen octahedral rotations, perovskite oxides can exhibit zone boundary transitions (ZBTs) either with $d{T}_{c}/dP>\phantom{\rule{0.16em}{0ex}}0$ or $d{T}_{c}/dP<\phantom{\rule{0.16em}{0ex}}0$. Synchrotron structural investigations at high pressure conditions place $\mathrm{YA}{\mathrm{l}}_{0.25}\mathrm{C}{\mathrm{r}}_{0.75}{\mathrm{O}}_{3}$ orthorhombic perovskite at the boundary of ZBTs. The absence of …

[Phys. Rev. B 95, 024110] Published Mon Jan 23, 2017

]]>First-principles density functional theory methods are used to investigate the structure, energetics, and vibrational motions of the neutral vacancy defect in diamond. The measured optical absorption spectrum demonstrates that the tetrahedral ${T}_{d}$ point group symmetry of pristine diamond is maintained…

[Phys. Rev. B 95, 014108] Published Fri Jan 20, 2017

]]>The load-controlled mode is routinely used in nanoindentation experiments. Yet there are no simulations or models that predict the generic features of force-displacement $F\text{\u2212}z$ curves, in particular, the existence of several displacement jumps of decreasing magnitude. Here, we show that the recently de…

[Phys. Rev. B 95, 014107] Published Thu Jan 19, 2017

]]>We report hafnium nitrides under pressure using first-principles evolutionary calculations. Metallic $P{6}_{3}/mmc$-HfN (calculated Vickers hardness 23.8 GPa) is found to be more energetically favorable than NaCl-type HfN at zero and high pressure. Moreover, NaCl-type HfN actually undergoes a phase transit…

[Phys. Rev. B 95, 020103(R)] Published Wed Jan 18, 2017

]]>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

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