Friction between sliding objects is a phenomenon so ubiquitous that it is easily forgotten how few of its microscopic details are properly understood. To gain new insight into the dynamical mechanism of sliding dissipation, the authors investigate a minimal model of a rigid slider traveling over a harmonic substrate. With the analytical tools of linear response theory, the authors obtain an expression for the dynamical friction that depends on known static physical quantities. This result sheds new light on the physical intertwining between dissipation and the phononic degrees of freedom of the substrate.

[Phys. Rev. B 97, 104104] Published Thu Mar 15, 2018

]]>Raman spectroscopy is employed to probe directly the soft rotation and tilting modes, which are two primary order parameters predicted in the hybrid improper ferroelectric material ${\mathrm{Ca}}_{3}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$. We observe a giant softening of the $107-{\mathrm{cm}}^{-1}$ octahedron tilting mode by $26\phantom{\rule{0.28em}{0ex}}{\mathrm{cm}}^{-1}$ on heating through the structu...

[Phys. Rev. B 97, 094104] Published Wed Mar 14, 2018

]]>A series of iron arsenides (e.g., ${\text{CaRbFe}}_{4}{\text{As}}_{4},{\text{SrCsFe}}_{4}{\text{As}}_{4}$) have been discovered recently, and have provoked a rise in superconductor searches in a different phase, known as the 1144 phase. For the presence of various chemical substitutions, it is believed that more 1144 compounds remain to be discove...

[Phys. Rev. B 97, 094105] Published Wed Mar 14, 2018

]]>To verify the first-order liquid-liquid transition (LLT) in liquid Cs reported by Falconi *et al.* [Phys. Rev. Lett. **94**, 125507 (2005).], the pressure dependence of liquid density was measured up to 5 GPa by an x-ray absorption method. The results showed that the density continuously increases over th...

[Phys. Rev. B 97, 100101(R)] Published Wed Mar 14, 2018

]]>It is well known that plastic deformation is a highly nonlinear dissipative irreversible phenomenon of considerable complexity. As a consequence, little progress has been made in modeling some well-known size-dependent properties of plastic deformation, for instance, calculating hardness as a functi...

[Phys. Rev. B 97, 104103] Published Mon Mar 12, 2018

]]>Laser-heated diamond-anvil cell (LHDAC) experiments reveal electronic changes in KBr at pressures between $\sim 13\u201381\phantom{\rule{0.28em}{0ex}}\mathrm{GPa}$ when heated to high temperatures that cause runaway heating to temperatures in excess of $\sim 5000\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. The drastic changes in absorption behavior of KBr are interpreted as rapid formation of...

[Phys. Rev. B 97, 094103] Published Fri Mar 09, 2018

]]>*Ab initio* density-functional calculations are used to investigate the response of four face-centered-cubic (fcc) high-entropy alloys (HEAs) to tensile and shear loading. The ideal tensile and shear strengths (ITS and ISS) of the HEAs are studied by employing first-principles alloy theory formulated ...

[Phys. Rev. B 97, 094102] Published Wed Mar 07, 2018

]]>Helium bubbles can form in a wide variety of materials and are of significance in a great variety of circumstances, ranging from electronics through nuclear physics or geology to outer-space exploration. However, their properties remain elusive, especially at the nanometer scale. Here, the authors study by means of transmission electron microscopy the structural modification and, simultaneously, the helium emission from individual nanosized bubbles in silicon during $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0.333em}{0ex}}s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u$ annealing. It is shown that, surprisingly, helium emission takes place at temperatures where bubble migration has barely begun. Analytical modeling of helium emission suggests that helium is in its solid state in the most highly pressurized bubbles.

[Phys. Rev. B 97, 104102] Published Wed Mar 07, 2018

]]>We report an observation of a phase transition in ${\mathrm{Ce}}_{3}{\mathrm{Rh}}_{4}{\mathrm{Sn}}_{13}$ with the transition temperature ${T}^{*}\simeq 350$ K by means of synchrotron x-ray powder diffraction, specific heat, electrical resistivity, Seebeck coefficient, thermal conductivity, as well as ${}^{119}\mathrm{Sn}$ nuclear magnetic resonance (NMR) measurements. Th...

[Phys. Rev. B 97, 094101] Published Tue Mar 06, 2018

]]>Solving the phase problem in x-ray crystallography has occupied a considerable scientific effort in the 20th century and led to great advances in structural science. Here we use x-ray ptychography to demonstrate an interference method which measures the phase of the beam transmitted through a crysta...

[Phys. Rev. B 97, 104101] Published Tue Mar 06, 2018

]]>Landau free-energy expansion parameters for $0.64\mathrm{Pb}\left(\mathrm{M}{\mathrm{g}}_{1/3}\mathrm{N}{\mathrm{b}}_{2/3}\right){\mathrm{O}}_{3}-0.36\mathrm{PbTi}{\mathrm{O}}_{3}$ single crystal were determined from the temperature-dependent polarization-electric field ($P-E$) hysteresis loops along ${\left[001\right]}_{C}$, the temperature-dependent dielectric constant ${\varepsilon}_{11}$, and the electric-field-induced tetragonal-rhom...

[Phys. Rev. B 97, 054114] Published Wed Feb 28, 2018

]]>Materials that are simultaneously transparent and electrically conductive play a key role in optoelectronic devices. Barium stannate has recently come to the forefront as a promising new transparent conductor, but its conductivity has been difficult to control. The authors have performed computational studies to determine the mechanisms that limit doping. They find that atomic-scale defects, such as vacancies in the crystal lattice, are responsible, but their formation can be controlled by tailoring the growth conditions. The authors also investigated related materials, such as strontium stannate and calcium stannate, which are transparent even in the ultraviolet. Calcium stannate is found to always be insulating, but guidelines are provided for maximizing the conductivity of the strontium compound.

[Phys. Rev. B 97, 054112] Published Mon Feb 26, 2018

]]>A phase-field model of a crystalline material is introduced to develop the necessary theoretical framework to study plastic flow due to dislocation motion. We first obtain the elastic stress from the phase-field crystal free energy under weak distortion and show that it obeys the stress-strain relat...

[Phys. Rev. B 97, 054113] Published Mon Feb 26, 2018

]]>The chemical reaction products of molecular hydrogen $\left({\mathrm{H}}_{2}\right)$ with selenium (Se) are studied by synchrotron x-ray diffraction (XRD) and Raman spectroscopy at high pressures. We find that a common ${\mathrm{H}}_{2}\mathrm{Se}$ is synthesized at 0.3 GPa using laser heating. Upon compression at 300 K, a crystal of the theoreticall...

[Phys. Rev. B 97, 064107] Published Mon Feb 26, 2018

]]>The magnetopolaron effect on shallow-impurity states in semiconductors is investigated when subjected simultaneously to a magnetic field and an intense terahertz laser field within the Faraday configuration. We use a time-dependent nonperturbative theory to describe electron interactions. The extern...

[Phys. Rev. B 97, 064108] Published Mon Feb 26, 2018

]]>The number of paramagnetic materials that undergo a structural phase transition is rather small, which can perhaps explain the limited understanding of the band Jahn-Teller mechanism responsible for this effect. Here we present a structural phase transition observed in paramagnetic ${\mathrm{Y}}_{2}\mathrm{In}$ at temperatu...

[Phys. Rev. B 97, 054111] Published Fri Feb 23, 2018

]]>Granular crystals are periodic structures of elastic beads arranged in crystal lattices. One important feature of granular crystals is that the interactions between beads can take place via noncentral contact forces, leading to the propagation of rotational and coupled rotational-translational waves...

[Phys. Rev. B 97, 060101(R)] Published Thu Feb 22, 2018

]]>Using first-principles calculations, we systematically study the elastic stiffness constants, mechanical properties, elastic wave velocities, Debye temperature, melting temperature, and specific heat of several thermodynamically stable crystal structures of ${\mathrm{Bi}}_{x}{\mathrm{Sb}}_{1-x}$ ($0<x<1$) binaries, which are...

[Phys. Rev. B 97, 054108] Published Tue Feb 20, 2018

]]>Tin titanate ($\mathrm{SnTi}{\mathrm{O}}_{3}$) has been notoriously impossible to prepare as a thin-film ferroelectric, probably because high-temperature annealing converts much of the $\mathrm{S}{\mathrm{n}}^{2+}$ to $\mathrm{S}{\mathrm{n}}^{4+}$. In the present paper, we show two things: first, perovskite phase $\mathrm{SnTi}{\mathrm{O}}_{3}$ can be prepared by atomic-layer deposition directly o...

[Phys. Rev. B 97, 054109] Published Tue Feb 20, 2018

]]>Ferroelectric materials are characterized by a spontaneous polar distortion. The behavior of such distortion in the presence of free charge is the key to the physics of metallized ferroelectrics in particular, and of structurally polar metals more generally. Using first-principles simulations, here ...

[Phys. Rev. B 97, 054107] Published Thu Feb 15, 2018

]]>$(\mathrm{Mg},\mathrm{Fe})\mathrm{Si}{\mathrm{O}}_{3}$ perovskite is the most abundant mineral of the Earth's lower mantle, and compounds with the perovskite structure are perhaps the most widely employed ceramics. Hence, they attract both geophysicists and material scientists. Several investigations attempted to predict their structural evo...

[Phys. Rev. B 97, 064106] Published Wed Feb 14, 2018

]]>We report an experimental and numerical study of femtosecond multipulse laser-induced densification in vitreous silica ($v-{\mathrm{SiO}}_{2}$) and its signature in Raman spectra. We compare the experimental findings to the recently developed molecular dynamics (MD) approach accounting for bond breaking due to lase...

[Phys. Rev. B 97, 054106] Published Tue Feb 13, 2018

]]>The *thermal lines* method for the evaluation of vibrational expectation values of electronic observables [B. Monserrat, Phys. Rev. B **93**, 014302 (2016)] was recently proposed as a physically motivated approximation offering balance between the accuracy of direct Monte Carlo integration and the low com...

[Phys. Rev. B 97, 054104] Published Mon Feb 12, 2018

]]>A hyperuniform many-body system is characterized by a structure factor $S\left(\mathit{k}\right)$ that vanishes in the small-wave-number limit or equivalently by a local number variance ${\sigma}_{N}^{2}\left(R\right)$ associated with a spherical window of radius $R$ that grows more slowly than ${R}^{d}$ in the large-$R$ limit. Thus, the hyperuniformity implies...

[Phys. Rev. B 97, 054105] Published Mon Feb 12, 2018

]]>Ferroelectric-ferromagnetic multiferroic composites are of great interest both from the scientific and technological standpoints. The extent of coupling between polarization and magnetization in such two-phase systems depends on how efficiently the magnetostrictive and electrostrictive/piezoelectric...

[Phys. Rev. B 97, 064103] Published Mon Feb 12, 2018

]]>With increasing temperature, metallic glasses (MGs) undergo first glass transition without pronounced structural change and then crystallization with distinct variation in structure and properties. The present study shows a structural change of short-range order induced by an electron-delocalization...

[Phys. Rev. B 97, 064104] Published Mon Feb 12, 2018

]]>We introduce a local order metric (LOM) that measures the degree of order in the neighborhood of an atomic or molecular site in a condensed medium. The LOM maximizes the overlap between the spatial distribution of sites belonging to that neighborhood and the corresponding distribution in a suitable ...

[Phys. Rev. B 97, 064105] Published Mon Feb 12, 2018

]]>Defect formation in LiF, which is used as an observation window in ramp and shock experiments, has significant effects on its transmission properties. Given the extreme conditions of the experiments it is hard to measure the change in transmission directly. Using molecular dynamics, we estimate the ...

[Phys. Rev. B 97, 054103] Published Thu Feb 08, 2018

]]>The Gibbs free energy is the fundamental thermodynamic potential underlying the relative stability of different states of matter under constant-pressure conditions. However, computing this quantity from atomic-scale simulations is far from trivial, so the potential energy of a system is often used a...

[Phys. Rev. B 97, 054102] Published Tue Feb 06, 2018

]]>We report high-pressure Raman, synchrotron x-ray diffraction, and electrical transport studies on Weyl semimetals NbP and TaP along with first-principles density functional theoretical (DFT) analysis. The frequencies of first-order Raman modes of NbP harden with increasing pressure and exhibit a slo...

[Phys. Rev. B 97, 064102] Published Mon Feb 05, 2018

]]>The $\mathrm{Cu}\phantom{\rule{0.16em}{0ex}}\mathrm{\Sigma}5$ grain boundary (GB) fracture process has been simulated by the first-principles computational tensile test. An additional metastable state has been discovered during tensile tests. The energy of ideal mirror-symmetric GBs continuously changes with tensile strains. However, at high strains, ...

[Phys. Rev. B 97, 054101] Published Fri Feb 02, 2018

]]>Key properties of nine possible defect sites in hexagonal boron nitride (h-BN), ${V}_{\mathrm{N}},{{V}_{\mathrm{N}}}^{-1},{\mathrm{C}}_{\mathrm{N}},{V}_{\mathrm{N}}{\mathrm{O}}_{2\mathrm{B}},{V}_{\mathrm{N}}{\mathrm{N}}_{\mathrm{B}},{V}_{\mathrm{N}}{\mathrm{C}}_{\mathrm{B}},{V}_{\mathrm{B}}{C}_{\mathrm{N}},{V}_{\mathrm{B}}{\mathrm{C}}_{\mathrm{N}}\mathrm{S}{\mathrm{i}}_{\mathrm{N}}$, and ${V}_{\mathrm{N}}{\mathrm{C}}_{\mathrm{B}}\mathrm{S}{\mathrm{i}}_{\mathrm{B}}$, are predicted using density-functional theory and are corrected by applying results from high-level *ab initio* calculations. Observed h-BN electron-paramagnetic resona...

[Phys. Rev. B 97, 064101] Published Thu Feb 01, 2018

]]>Single-crystal x-ray diffraction studies with synchrotron radiation on the honeycomb iridate $\alpha -{\mathrm{Li}}_{2}{\mathrm{IrO}}_{3}$ reveal a pressure-induced structural phase transition with symmetry lowering from monoclinic to triclinic at a critical pressure of ${P}_{c}=3.8$ GPa. According to the evolution of the lattice parameters ...

[Phys. Rev. B 97, 020104(R)] Published Wed Jan 31, 2018

]]>We use a combination of symmetry analysis and high-throughput density functional theory calculations to search for new ferroelectric materials. We use two search strategies to identify candidate materials. In the first strategy, we start with nonpolar materials and look for unrecognized energy-lower...

[Phys. Rev. B 97, 024115] Published Wed Jan 31, 2018

]]>Uniaxial ferroelectric $\mathrm{BaT}{\mathrm{i}}_{2}{\mathrm{O}}_{5}$ with a Curie temperature ${T}_{\mathrm{C}}$ of 743 K was investigated to clarify its paraelectric-ferroelectric phase-transition behavior. The mechanism is discussed on the basis of the structure from short to long ranges determined by synchrotron x-ray diffraction and the lattice dyn...

[Phys. Rev. B 97, 024116] Published Wed Jan 31, 2018

]]>We study the existence of guided acoustic modes in layered structures whose phase velocity is higher than that of bulk waves in a solid substrate or an adjacent fluid half space, which belong to the class of bound states in the radiation continuum (BICs). We demonstrate that in contrast to the elect...

[Phys. Rev. B 97, 014108] Published Tue Jan 30, 2018

]]>Shock wave interactions with defects, such as pores, are known to play a key role in the chemical initiation of energetic materials. The shock response of hexanitrostilbene is studied through a combination of large-scale reactive molecular dynamics and mesoscale hydrodynamic simulations. In order to...

[Phys. Rev. B 97, 014109] Published Tue Jan 30, 2018

]]>High-melting-point oxides of chemical formula $AB{\mathrm{O}}_{3}$ with $A=\mathrm{Ca}$, Sr, Ba and $B=\mathrm{Zr}$, Hf are investigated as a function of hydrostatic pressure up to 200 GPa by combining first-principles calculations with a particle swarm optimization method. Ca- and Sr-based systems: (1) first undergo a reconstructive ph...

[Phys. Rev. B 97, 020103(R)] Published Tue Jan 30, 2018

]]>In this work, we quantify oxygen self-diffusion in monoclinic-phase zirconium oxide as a function of temperature and oxygen partial pressure. A migration barrier of each type of oxygen defect was obtained by first-principles calculations. Random walk theory was used to quantify the diffusivities of ...

[Phys. Rev. B 97, 024114] Published Mon Jan 29, 2018

]]>An important theoretical criterion to evaluate the ductility of metals with a body-centered cubic (bcc) lattice is the mechanical failure mode of their perfect crystals under tension along $\langle 100\rangle $ directions. When the tensile stress reaches the ideal tensile strength, the pure W crystal fails by a cle...

[Phys. Rev. B 97, 014107] Published Fri Jan 26, 2018

]]>From superconductivity to magnetoelectricity, perovskite oxides exhibit a wealth of appealing physical properties, often controlled by subtle structural details. Especially critical are the ‘tilt’ distortion modes involving rotations of the oxygen octahedra that constitute the backbone of the perovskite lattice, which motivates today’s interest in better understanding and tuning such tilts. Here, the authors present a thorough first-principles investigation of the energy landscape relevant to this matter, revealing the main competitors among different tilt modes as well as their trends across the perovskite family.

[Phys. Rev. B 97, 024113] Published Fri Jan 26, 2018

]]>Pressure induced solid-solid reconstructive phase transitions for graphite-diamond, and wurtzite-rocksalt in GaN and AlN occur at significantly higher pressure than expected from equilibrium coexistence and their transition paths are always inconsistent with each other. These indicate that the under...

[Phys. Rev. B 97, 014106] Published Thu Jan 25, 2018

]]>We have used synchrotron x-ray and Raman spectroscopic studies combined with molecular dynamics to investigate the ${\mathrm{I}}_{2}-{\mathrm{H}}_{2}$ system at high pressure. By laser heating the mixture above 25 GPa we synthesized the molecular compound $\mathrm{HI}{\left({\mathrm{H}}_{2}\right)}_{13}$, with the ${AB}_{13}$ structure type and unusually high volumetric hydro...

[Phys. Rev. B 97, 024111] Published Wed Jan 24, 2018

]]>Iterative neural-network-based three-dimensional structural optimization of atomic positions over tens of nanometers is performed using transmission electron microscope (TEM) diffraction data simulated from density functional theory (DFT) all-electron densities, thus retrieving parameter variations ...

[Phys. Rev. B 97, 024112] Published Wed Jan 24, 2018

]]>Materials with properties that are modulated in time are known to display wave phenomena showing energy increasing with time, with the rate mediated by the modulation. Until now there has been no accounting for material dissipation, which clearly counteracts energy growth. This paper provides an exa...

[Phys. Rev. B 97, 014105] Published Mon Jan 22, 2018

]]>Coordination-related, two-dimensional (2D) structural phase transitions are a fascinating facet of two-dimensional materials with structural degeneracies. Nevertheless, a unified theoretical account of these transitions remains absent, and the following points are established through *ab initio* molec...

[Phys. Rev. B 97, 024110] Published Mon Jan 22, 2018

]]>In this paper we investigate a hybrid quantum system comprising a mechanical oscillator coupled via magnetic induced electromotive force to an $LC$ resonator. We derive the Lagrangian and Hamiltonian for this system and find that the interaction can be described by a charge-momentum coupling with a st...

[Phys. Rev. B 97, 024109] Published Fri Jan 19, 2018

]]>The authors propose here the first experimentally viable scheme of a topological insulator for sound waves at the nanoscale. This significantly advances the field of nanoscale phononics, adding helical waveguides to its toolbox. The proposed device could hardly be simpler as it relies purely on a geometrical design, based on the “snowflake” phononic crystal that has already been demonstrated experimentally.

[Phys. Rev. B 97, 020102(R)] Published Thu Jan 18, 2018

]]>A method is introduced to stochastically generate crystal structures with defined structural characteristics. Reasonable quotient graphs for symmetric crystals are constructed using a random strategy combined with space group and graph theory. Our algorithm enables the search for large-size and comp...

[Phys. Rev. B 97, 014104] Published Wed Jan 17, 2018

]]>Despite more than 50 years of investigation, the understanding of the metal-insulator transition in ${\mathrm{VO}}_{2}$ remains incomplete and requires additional experimental and theoretical works. Using Raman scattering under pressure, we first confirm the known transition around 11 GPa affecting the V orbital oc...

[Phys. Rev. B 97, 024107] Published Wed Jan 17, 2018

]]>The temperature-induced antiferrodistortive (AFD) structural phase transitions in ${\mathrm{CaMnO}}_{3}$, a typical perovskite oxide, are studied using first-principles density functional theory calculations. These transitions are caused by tilting of the ${\mathrm{MnO}}_{6}$ octahedra that are related to unstable phonon modes in ...

[Phys. Rev. B 97, 024108] Published Wed Jan 17, 2018

]]>The two-dimensional $XY$ model is the first well-studied system with topological point defects. On the other hand, although topological line defects are common in three-dimensional systems, the evolution mechanism of line defects is not fully understood. The six domains in hexagonal manganites converg...

[Phys. Rev. B 97, 020101(R)] Published Tue Jan 16, 2018

]]>Plate impact experiments in the 100–250 GPa pressure range were done on a $\langle 100\rangle $ single-crystal MgO preheated before compression to 1850 K. Hot Mo(driver)-MgO targets were impacted with Mo or Ta flyers launched by the Caltech two-stage light-gas gun up to 7.5 km/s. Radiative temperatures and shock ve...

[Phys. Rev. B 97, 024106] Published Tue Jan 16, 2018

]]>It is generally claimed that physical processes which display scale-invariant power-law distributions are subjected to a dynamic criticality that prohibits a well-defined kinetic law. In this paper, we demonstrate the coexistence of these two apparently contradicting behaviors during the same physic...

[Phys. Rev. B 97, 014103] Published Fri Jan 12, 2018

]]>We demonstrate magnetic-field sensing using an ensemble of nitrogen-vacancy centers by recording the variation in the pump-light absorption due to the spin-polarization dependence of the total ground-state population. Using a 532 nm pump laser, we measure the absorption of native nitrogen-vacancy ce...

[Phys. Rev. B 97, 024105] Published Thu Jan 11, 2018

]]>Understanding the underlying mechanism of the nanostructure-mediated high diffusivity of H in Pd is of recent scientific interest and also crucial for industrial applications. Here, we present a decisive scenario explaining the emergence of the fast lattice-diffusion mode of interstitial H in face-c...

[Phys. Rev. B 97, 014102] Published Wed Jan 10, 2018

]]>Ultrafast laser irradiation causes intense electronic excitations in materials, leading to transient high temperatures and pressures. Here, we show that ultrafast laser irradiation drives an irreversible cubic-to-monoclinic phase transformation in ${\mathrm{Ln}}_{2}{\mathrm{O}}_{3}\phantom{\rule{4pt}{0ex}}\left(\mathrm{Ln}=\mathrm{Er}\u2013\mathrm{Lu}\right)$, and explore the mechanism by which ...

[Phys. Rev. B 97, 024104] Published Wed Jan 10, 2018

]]>Here we examine the role of anharmonicity in the elastic constants of bulk metallic glasses and develop an anharmonic model to consider the effects of both pressure and temperature across the glass transition. By comparing against reported experimental data and elastic constants obtained from molecu...

[Phys. Rev. B 97, 014101] Published Tue Jan 09, 2018

]]>We have revealed $\mathrm{S}{\mathrm{b}}_{2}{\mathrm{S}}_{3}$ to have two phase transitions and to undergo metallization using a diamond anvil cell at around 5.0, 15.0, and 34.0 GPa, respectively. These results were obtained on the basis of high-pressure Raman spectroscopy, temperature-dependent conductivity measurements, atomic force mi...

[Phys. Rev. B 97, 024103] Published Mon Jan 08, 2018

]]>Using the Landau-Ginzburg-Devonshire theory, we considered the impact of the flexoelectrochemical coupling on the size effects in polar properties and phase transitions of thin ferroelectric films with a layer of elastic defects. We investigated a typical case, when defects fill a thin layer below t...

[Phys. Rev. B 97, 024102] Published Fri Jan 05, 2018

]]>The addition of transition-metal (TM) elements into the ${\gamma}^{\prime}$ precipitate phase of a Ni-based single-crystal superalloy can significantly affect its mechanical properties, including the intrinsic mechanical property of compressive strength. Using first-principles density functional calculations, the ef...

[Phys. Rev. B 97, 024101] Published Thu Jan 04, 2018

]]>We report comprehensive x-ray absorption spectroscopy studies at both the Ga $K$ edge and Yb ${L}_{2}$ edge to elucidate the local structure of Ga and Yb dopants in ${\mathrm{Yb}}_{x}{\mathrm{Ga}}_{y}{\mathrm{Co}}_{4}{\mathrm{Sb}}_{12}$. Our extended x-ray absorption fine structure (EXAFS) data confirm that Ga atoms occupy two crystallographic sites: one is the $24g$...

[Phys. Rev. B 96, 224107] Published Fri Dec 29, 2017

]]>In this paper, we examine, in terms of the classical nucleation theory, how the strengthening of the attractive intermolecular interactions influences the crystallization process for systems like Lennard-Jones at different isobaric conditions. For this purpose, we modify the standard Lennard-Jones p...

[Phys. Rev. B 96, 224106] Published Thu Dec 28, 2017

]]>On the basis of a phenomenological Landau model combined with comprehensive experimental studies, the magnetostructural transition behavior and field induced caloric effects for NiMnGaCu Heusler alloys have been investigated. In ${\mathrm{Ni}}_{50}{\mathrm{Mn}}_{25-x}{\mathrm{Ga}}_{25}{\mathrm{Cu}}_{x}$ alloys with $x=5.5$, 6, and 6.5, both magnetocaloric en...

[Phys. Rev. B 96, 224105] Published Wed Dec 27, 2017

]]>An allotrope of nitrogen formed solely by N-N single bonds is predicted to exist between 100 and 150 GPa. The crystal structure has the *Pccn* symmetry and is characterized by a distorted tetrahedral network consisting of fused ${\mathrm{N}}_{8},{\mathrm{N}}_{10}$, and ${\mathrm{N}}_{12}$ rings. Stability of this structure is established by phon...

[Phys. Rev. B 96, 224104] Published Tue Dec 26, 2017

]]>This *in situ* neutron-diffraction study on antiferroelectric (AFE) $\mathrm{P}{\mathrm{b}}_{0.99}\left(\mathrm{N}{\mathrm{b}}_{0.02}\mathrm{Z}{\mathrm{r}}_{0.65}\mathrm{S}{\mathrm{n}}_{0.28}\mathrm{T}{\mathrm{i}}_{0.05}\right){\mathrm{O}}_{3}$ polycrystalline materials describes systematic structural and associated preferred orientation changes as a function of applied electric field and temperature. It is found that the pristine AFE phase...

[Phys. Rev. B 96, 214108] Published Thu Dec 21, 2017

]]>Recently, hydrogen sulfide has attracted enormous attention due to the record high-temperature superconductivity of ${\text{H}}_{3}\text{S}$ with ${T}_{c}=203$ K at a pressure of 155 GPa. In addition to ${\text{H}}_{3}\text{S}$, there are many theoretically and experimentally confirmed compositions and crystal structures forming under high pressur...

[Phys. Rev. B 96, 220101(R)] Published Thu Dec 21, 2017

]]>A semiclassical approach that incorporates quantum mechanical behavior of heat capacity in direct caloric effect simulations is proposed. Application of this methodology to study the electrocaloric effect in prototypical ferroelectrics ${\mathrm{PbTiO}}_{3}$ and ${\mathrm{BaTiO}}_{3}$ reveals severe underestimation of electrocal...

[Phys. Rev. B 96, 214107] Published Tue Dec 19, 2017

]]>The interaction of point defects with an external stress field or with other structural defects is usually well described within continuum elasticity by the elastic dipole approximation. Extraction of the elastic dipoles from atomistic simulations is therefore a fundamental step to connect an atomis...

[Phys. Rev. B 96, 224103] Published Tue Dec 19, 2017

]]>We investigate the surface stress of solid-liquid diffusive interfaces at equilibrium using the phase field crystal model in two dimensions. To analytically study the surface energy dependence on elastic strains, we employ the amplitude equation formalism and recast the free energy functional in ter...

[Phys. Rev. B 96, 214106] Published Fri Dec 15, 2017

]]>The paraelectric-ferroelectric transition in $\mathrm{CdTi}{\mathrm{O}}_{3}$ has been monitored using high-resolution neutron diffraction data. This necessitated preparing a sample enriched in ${}^{114}\mathrm{Cd}$. A subtle, but significant, anisotropy in the thermal expansion of the lattice parameters for $\mathrm{CdTi}{\mathrm{O}}_{3}$ associated with the trans...

[Phys. Rev. B 96, 214105] Published Wed Dec 13, 2017

]]>Although many works have been devoted to the order-disorder transition in carbon-supersaturated α-Fe, all seem to have overlooked the temperature hysteresis phenomenon occurring around the critical temperature. It is shown, from a mean-field model based on the elasticity theory of point defects, tha...

[Phys. Rev. B 96, 214104] Published Tue Dec 12, 2017

]]>We use scattering theory to study the spatial resolution achievable in vibrational energy loss spectroscopy using a focused beam of high-energy ($\sim 100$ keV) electrons. We first outline a theory for calculating vibrational-spectroscopic images of crystalline or noncrystalline materials at nanometer spa...

[Phys. Rev. B 96, 224102] Published Mon Dec 11, 2017

]]>Hard-mode Raman spectroscopy was applied to analyze the temperature-induced transformation processes in perovskite-type $\left({\mathrm{ABO}}_{3}\right)$ single crystals of $\left(1\text{\u2212}x\right){\mathrm{Na}}_{0.5}{\mathrm{Bi}}_{0.5}{\mathrm{TiO}}_{3}\text{\u2212}x{\mathrm{BaTiO}}_{3}$ (NBT-$x\mathrm{BT})$ in a wide temperature range between 100 and 1010 K and a composition range of $x=0\u20130.074$ across the morphotropic phas...

[Phys. Rev. B 96, 214102] Published Fri Dec 08, 2017

]]>We present a detailed structure solution for the $16\text{\u2212}\AA $ decagonal quasicrystal in the Al-Pd-Mn system by means of cluster decoration and *ab initio* energy minimization. It is based on structure models of the $\varepsilon $ and other approximant phases. The $\varepsilon $ phases can be represented as subsets of a hexagon-boat-st...

[Phys. Rev. B 96, 214103] Published Fri Dec 08, 2017

]]>The phase diagram of 1$T$-TaS${}_{2}$ involves many different solid-state phases, including several different kinds of charge-density-wave (CDW) phase both commensurate and incommensurate with the underlying lattice. Recent experiments have shown that it is possible to drive transitions between these phases with intense femtosecond pulses of light. This work focuses on the light-driven transition from the nearly commensurate CDW phase to the incommensurate phase, using time-resolved x-ray diffraction. The authors find that the new incommensurate domains grow in a self-similar way. They also employ a double-pump method to study the dynamics and stability of the novel incommensurate phase during growth.

[Phys. Rev. B 96, 224101] Published Wed Dec 06, 2017

]]>All carbon materials, e.g., amorphous carbon (a-C) coatings and ${\mathrm{C}}_{60}$ fullerene thin films, play an important role in short-wavelength free-electron laser (FEL) research motivated by FEL optics development and prospective nanotechnology applications. Responses of a-C and ${\mathrm{C}}_{60}$ layers to the extreme ultr...

[Phys. Rev. B 96, 214101] Published Mon Dec 04, 2017

]]>The plastic deformation of crystalline materials is usually modeled as smoothly progressing in space and time, yet modern studies show intermittency in the deformation dynamics of single-crystals arising from avalanche behavior of dislocation ensembles under uniform applied loads. However, once the ...

[Phys. Rev. B 96, 174116] Published Thu Nov 30, 2017

]]>We define a structural parameter, called atomic bond length deviation ($\mathrm{BL}{\mathrm{D}}_{\mathrm{i}}$), to characterize structural heterogeneity of CuZr melt and metallic glass (MG). Molecular dynamics simulations have been performed to explore the average $\mathrm{BL}{\mathrm{D}}_{\mathrm{i}}$ of the system evolution with temperature during $\mathrm{C}{\mathrm{u}}_{64}\mathrm{Z}{\mathrm{r}}_{36}$ and $\mathrm{C}{\mathrm{u}}_{\mathrm{5...}}$

[Phys. Rev. B 96, 174112] Published Mon Nov 27, 2017

]]>From the new infrared (IR) reflectivity and time-domain terahertz spectra combined with available high-frequency dielectric data above the megahertz range in a broad temperature range of 10 to 900 K, a full picture of the soft- and central-mode behavior in the classical relaxor ferroelectric $\mathrm{Pb}(\mathrm{M}{\mathrm{g}}_{1/\mathrm{...}}$

[Phys. Rev. B 96, 174113] Published Mon Nov 27, 2017

]]>We report the results of ambient temperature high-pressure synchrotron-based x-ray diffraction, Raman, and electrical resistance study of $\mathrm{Cs}{\mathrm{I}}_{3}$ up to 29, 25, and 8 GPa, respectively, and confirm three-phase transitions under quasihydrostatic conditions. The ambient orthorhombic (space group (SG): *Pnm...*

[Phys. Rev. B 96, 174114] Published Mon Nov 27, 2017

]]>The influence of nanoscale cavities on the fracture of the $\mathrm{\Sigma}33\left\{554\right\}\left[110\right]$ symmetrical tilt grain boundary is studied by atomistic simulations. The crack crystallography is chosen such that dislocation emission is easy. A transition from a ductile behavior of the tip to a brittle one is obtained for a...

[Phys. Rev. B 96, 174115] Published Mon Nov 27, 2017

]]>Pressure-induced polarization switching in ferroelectric thin films has emerged as a powerful method for domain patterning, allowing us to create predefined domain patterns on free surfaces and under thin conductive top electrodes. However, the mechanisms for pressure-induced polarization switching ...

[Phys. Rev. B 96, 184109] Published Mon Nov 27, 2017

]]>The dynamics of the phase transition in antiferroelectric ${\mathrm{PbZrO}}_{3}$ which is the subject of a decades-long debate, is examined using first-principles-based simulations. This is achieved through the development of a computational approach that allows calculations of generalized complex susceptibilities...

[Phys. Rev. B 96, 184110] Published Mon Nov 27, 2017

]]>Lead-halide organic-inorganic perovskites consist of an inorganic host framework with an organic molecule occupying the interstitial space. The structure and dynamics of these materials have been heavily studied recently due to interest in their exceptional photovoltaic properties. We combine inelas...

[Phys. Rev. B 96, 174111] Published Wed Nov 22, 2017

]]>We present an extended Tersoff potential for boron nitride (BN-ExTeP) for application in large scale atomistic simulations. BN-ExTeP accurately describes the main low energy B, N, and BN structures and yields quantitatively correct trends in the bonding as a function of coordination. The proposed ex...

[Phys. Rev. B 96, 184108] Published Mon Nov 20, 2017

]]>The work describes a first-principles-based computational strategy for studying structural phase transitions, and in particular, for determination of the so-called Landau-Devonshire potential—the classical zero-temperature limit of the Gibbs energy, expanded in terms of order parameters. It exploits...

[Phys. Rev. B 96, 174110] Published Fri Nov 17, 2017

]]>The local dynamics of the lead-free relaxor $0.964{\mathrm{Na}}_{1/2}{\mathrm{Bi}}_{1/2}{\mathrm{TiO}}_{3}-0.036{\mathrm{BaTiO}}_{3}$ (NBT-3.6BT) have been investigated by a combination of quasielastic neutron-scattering (QENS) and *ab initio* molecular dynamics simulations. In a previous paper, we were able to show that the tetragonal platelets in the micro...

[Phys. Rev. B 96, 184107] Published Wed Nov 15, 2017

]]>Measurement of the Hugoniot and sound velocity provides information on the bulk modulus and Grüneisen parameter of a material at extreme conditions. The capability to launch multilayered (copper/aluminum) flyer plates at velocities in excess of 20 km/s with the Sandia Z accelerator has enabled high-...

[Phys. Rev. B 96, 174109] Published Mon Nov 13, 2017

]]>The mechanical force from light—radiation pressure—provides an intrinsically nonlinear interaction. Consequently, optomechanical systems near their steady state, such as the canonical optical spring, can display nonanalytic behavior as a function of external parameters. This nonanalyticity, a key fe...

[Phys. Rev. B 96, 184106] Published Mon Nov 13, 2017

]]>We investigate the effects of Fe and Co substitutions on the phase stability of the martensitic phase and mechanical, electronic, and magnetic properties of the magnetic shape memory system ${\mathrm{Mn}}_{2}\mathrm{NiGa}$ by first-principles density functional theory calculations. The evolution of these aspects upon substi...

[Phys. Rev. B 96, 174107] Published Fri Nov 10, 2017

]]>Neutron and x-ray scattering measurements were performed on $\left(\mathrm{N}{\mathrm{a}}_{1/2}\mathrm{B}{\mathrm{i}}_{1/2}\right)\mathrm{Ti}{\mathrm{O}}_{3}\text{\u2212}x\phantom{\rule{0.28em}{0ex}}\mathrm{at}\%\mathrm{BaTi}{\mathrm{O}}_{3}$ (NBT-$x\mathrm{BT}$) single crystals ($x=4$, 5, 6.5, and 7.5) across the morphotropic phase boundary (MPB), as a function of both composition and temperature, and probing both structural and dynamical aspects. In addition to ...

[Phys. Rev. B 96, 174108] Published Fri Nov 10, 2017

]]>A force-matched spline-based empirical potential based on the modified embedded-atom method is fit to an extensive database of highly converged density functional theory calculations for titanium-niobium alloys with an evolutionary algorithm. Consistency with experiment and existing models is verifi...

[Phys. Rev. B 96, 184105] Published Fri Nov 10, 2017

]]>We present high-energy x-ray diffraction studies on the structural phases of an optimal high-${T}_{c}$ superconductor ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4+y}$ tailored by co-hole-doping. This is specifically done by varying the content of two very different chemical species, Sr and O, respectively, in order to study the influence o...

[Phys. Rev. B 96, 174106] Published Thu Nov 09, 2017

]]>First-principles molecular dynamics (FPMD) simulations are performed on 6 and 12% Na in dense liquid N. A detailed description of structural and electronic properties leading to an understanding of the effect of Na doping on the polymerization phase transition of N is presented. Compression of the m...

[Phys. Rev. B 96, 184104] Published Thu Nov 09, 2017

]]>Under mechanical loading, crystalline solids deform elastically, and subsequently yield and fail via plastic deformation. Thus crystalline materials experience two mechanical regimes: elasticity and plasticity. Here, we provide numerical and theoretical evidence to show that metal nanoplates exhibit...

[Phys. Rev. B 96, 184103] Published Tue Nov 07, 2017

]]>We study the two-step spin crossover in a double-layered elastic model based on transition metal complexes each taking high spin (HS) and low spin (LS) states. Here, only the simplest elastic interactions between adjacent molecules are considered, and the system is exposed to the external pressure w...

[Phys. Rev. B 96, 174104] Published Mon Nov 06, 2017

]]>The carbon vacancy in $4H$-SiC is a powerful minority carrier recombination center in as-grown material and a major cause of degradation of SiC-based devices. Despite the extensiveness and maturity of the literature regarding the characterization and modeling of the defect, many fundamental questions ...

[Phys. Rev. B 96, 174105] Published Mon Nov 06, 2017

]]>We measure the onset of decomposition of silicon carbide, SiC, to silicon and carbon (e.g., diamond) at high pressures and high temperatures in a laser-heated diamond-anvil cell. We identify decomposition through x-ray diffraction and multiwavelength imaging radiometry coupled with electron microsco...

[Phys. Rev. B 96, 174102] Published Fri Nov 03, 2017

]]>Direct experimental insights into the structural and dynamical mechanisms for ferroelectric β to paraelectric α phase transition in a poled PVDF-TrFE copolymer is obtained from *in situ* x-ray diffraction and quasielastic neutron scattering measurements at high temperatures. It is observed that the β-...

[Phys. Rev. B 96, 174103] Published Fri Nov 03, 2017

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