Selenium is the only easily vitrified elementary substance. Numerous experimental studies of glassy Se ($g$-Se) at high pressures show a large spread in the data on the compressibility and electrical resistivity of $g$-Se. Furthermore, H. Liu *et al.* [Proc. Natl. Acad. Sci. USA **105**, 13229 (2008)] have ar...

[Phys. Rev. B 96, 134111] Published Tue Oct 17, 2017

]]>Bulk Au-Fe alloys separate into Au-based fcc and Fe-based bcc phases, but ${\mathrm{L}1}_{0}$ and ${\mathrm{L}1}_{2}$ orderings were reported in single-phase Au-Fe nanoparticles. Motivated by these observations, we study the structural and ordering energetics in this alloy by combining density functional theory (DFT) calculations ...

[Phys. Rev. B 96, 134109] Published Mon Oct 16, 2017

]]>We present *in situ* high-pressure synchrotron x-ray diffraction (XRD) and electrical transport measurements on quasi-one-dimensional single-crystal $\mathrm{Ti}{\mathrm{S}}_{3}$ up to 29.9–39.0 GPa in diamond-anvil cells, coupled with first-principles calculations. Counterintuitively, the conductive behavior of semiconductor...

[Phys. Rev. B 96, 134110] Published Mon Oct 16, 2017

]]>Scandium hydrides at high pressures have been investigated by using *ab initio* density functional calculations. Although the stable scandium hydride so far known to have the highest content rate of hydrogen is ${\mathrm{ScH}}_{3}$, other more hydrogen-rich compounds are found to be possible at high pressures. These ...

[Phys. Rev. B 96, 144108] Published Mon Oct 16, 2017

]]>Relaxor ferroelectric materials, such as $\mathrm{Pb}\left[{\left(\mathrm{M}{\mathrm{g}}_{0.33}\mathrm{N}{\mathrm{b}}_{0.67}\right)}_{1\text{\u2212}x}\mathrm{T}{\mathrm{i}}_{x}\right]{\mathrm{O}}_{3}$ (PMN-PT) with generic stoichiometry, undergo a ferroelectric-to-paraelectric phase transition as a function of temperature. The exact transition characterized by Curie temperature (${T}_{c}$) varies as a function of chemistry ($x$), i.e., th...

[Phys. Rev. B 96, 134108] Published Fri Oct 13, 2017

]]>A 1D anharmonic chain with a single impurity particle is used to study the vibrational energy localization. Numerical and asymptotic solutions for the symmetric anharmonic localized mode are both presented. The numerical results reveal that the energy localization strengthens with decreasing impurit...

[Phys. Rev. B 96, 144107] Published Fri Oct 13, 2017

]]>The spatiotemporal dynamics of the spin transition have been thoroughly investigated in single crystals of the mononuclear spin-crossover (SCO) complex $\left[\mathrm{Fe}\left(\mathrm{HB}\right(\mathrm{tz}{)}_{3}{)}_{2}\right]$ ($\mathrm{tz}=1,2$,4-triazol-1-yl) by optical microscopy. This compound exhibits an abrupt spin transition centered at 334 K with a narrow therm...

[Phys. Rev. B 96, 134106] Published Wed Oct 11, 2017

]]>Using the conventional macroscopic description of the bulk photovoltaic effect we analyze the light-induced currents and electric fields arising in the optical configuration with a continuous bottom electrode and a small circular top electrode. This scheme is relevant to recent experiments on the ti...

[Phys. Rev. B 96, 134107] Published Wed Oct 11, 2017

]]>We report a detailed single-crystal and powder neutron diffraction study of ${\mathrm{Co}}_{2}{\mathrm{TiO}}_{4}$ and ${\mathrm{Co}}_{2}{\mathrm{SnO}}_{4}$ between the temperature 1.6 and 80 K to probe the spin structure in the ground state. For both compounds the strongest magnetic intensity was observed for the (111)${}_{\text{M}}$ reflection due to ferrimagnetic orderi...

[Phys. Rev. B 96, 144104] Published Wed Oct 11, 2017

]]>Through high-pressure Raman spectroscopy and x-ray diffraction experiments, we have investigated the formation, stability field, and structure of hydrogen iodide (HI). Hydrogen iodide is synthesized by the reaction of molecular hydrogen and iodine at room temperature and at a pressure of 0.2 GPa. Up...

[Phys. Rev. B 96, 144105] Published Wed Oct 11, 2017

]]>Hexagonal boron nitride (hBN) is a wide-band-gap semiconductor with applications including gate insulation layers in graphene transistors, far-ultraviolet light emitting devices and as hydrogen storage media. Due to its complex microstructure, defects in hBN are challenging to identify. Here, we com...

[Phys. Rev. B 96, 144106] Published Wed Oct 11, 2017

]]>Negative thermal expansion coefficients ($\alpha $) are found in the fcc and cI16 (a distorted bcc structure) phases of sodium at pressures above 90 GPa from first principles. At room temperature, the most significant negative $\alpha $ of about $-4.5\times {10}^{-6}\phantom{\rule{4pt}{0ex}}{\mathrm{K}}^{-1}$ is predicted in fcc sodium at 120 GPa, which represents t...

[Phys. Rev. B 96, 134104] Published Tue Oct 10, 2017

]]>Monitoring structural changes in ferroelectric thin films during electric field induced polarization switching is important for a full microscopic understanding of the coupled motion of charges, atoms, and domain walls in ferroelectric nanostructures. We combine standard ferroelectric test sequences...

[Phys. Rev. B 96, 134105] Published Tue Oct 10, 2017

]]>Within the framework of a realistic multiband $p-d$ model, we derived an effective Hamiltonian to describe the exchange interaction effects near the spin crossover in magnetic Mott-Hubbard insulators under pressure. It is shown that the single-ion mechanism of spin crossover under the change in the cr...

[Phys. Rev. B 96, 134103] Published Mon Oct 09, 2017

]]>Controlling and manipulating the topological state represents an important topic in condensed matters for both fundamental researches and applications. In this work, we focus on the evolution of a real-space topological domain structure in hexagonal manganites driven by electric field, using the ana...

[Phys. Rev. B 96, 144103] Published Mon Oct 09, 2017

]]>By using the density functional theory plus $U$ (DFT+$U$) method and taking spin-orbit coupling into account, we investigate the electronic and phonon properties of ${\mathrm{Pu}}_{3}\mathrm{Ga}$. Most interestingly, we find that there is a significant phonon softening in the transverse acoustic branch at the $L$ point in the Bri...

[Phys. Rev. B 96, 134102] Published Wed Oct 04, 2017

]]>Guided elastic waves in homogeneous isotropic plates exhibit conical dispersion at zero wave number for discrete values of Poisson's ratio where accidental degeneracy between longitudinal and transverse thickness resonances occur. Waves excited at the coincidence frequency have the infinite phase ve...

[Phys. Rev. B 96, 144101] Published Wed Oct 04, 2017

]]>Hybrid quantum/classical techniques can flexibly couple *ab initio* simulations to an empirical or elastic medium to model materials systems that cannot be contained in small periodic supercells. However, due to electronic nonlocality, a total energy cannot be defined, meaning energy barriers cannot b...

[Phys. Rev. B 96, 144102] Published Wed Oct 04, 2017

]]>Using laser-generated shock waves, we have measured pressure, density, and temperature of LiH on the principal Hugoniot between 260 and 1100 GPa (2.6–11 Mbar) and on a second-shock Hugoniot up to 1400 GPa to near fivefold compression, extending the maximum pressure reached in non-nuclear experiments...

[Phys. Rev. B 96, 134101] Published Mon Oct 02, 2017

]]>Using the Landau-Ginzburg-Devonshire theory and one component approximation, we examined the conditions of the soft acoustic phonon mode (**A**-mode) appearance in a ferroelectric (FE) depending on the magnitude of the flexoelectric coefficient $f$ and temperature $T$. If the flexocoefficient $f$ is equal to ...

[Phys. Rev. B 96, 094111] Published Fri Sep 29, 2017

]]>Boron nitride polymorphs hold great promise for integration into electronic and optoelectronic devices requiring ultrawide band gaps. We use first-principles calculations to examine the prospects for $p$-type doping of hexagonal ($h-\mathrm{BN}$), wurtzite ($wz-\mathrm{BN}$), and cubic ($c-\mathrm{BN}$) boron nitride. Group-IV elemen...

[Phys. Rev. B 96, 100102(R)] Published Fri Sep 29, 2017

]]>The local atomic geometries in ${\mathrm{Ba}}_{0.5}{\mathrm{Sr}}_{0.5}{\mathrm{TiO}}_{3}$ thin films grown on MgO(001) substrates have been determined by Ti $1s$ near-edge x-ray-absorption fine-structure measurements and density-functional-theory calculations. The accuracy of the atomic geometries predicted by density-functional theory is demon...

[Phys. Rev. B 96, 104111] Published Thu Sep 28, 2017

]]>Solid ${\mathrm{NH}}_{4}\mathrm{F}$ displays intriguing parallels with ice despite its apparently ionic character. Here we investigate its phase diagram in low-temperature and high-pressure regions using Raman spectroscopy, x-ray diffraction, and *ab initio* structure search calculations. We focus on the high-pressure cubic ...

[Phys. Rev. B 96, 094110] Published Mon Sep 25, 2017

]]>Time-space modulated media are realized by periodically modulating parameters of the media in both time and space. In this paper, we study frequency conversion induced by time-space modulated media. Two types of frequency conversion are theoretically and numerically demonstrated; their underlying me...

[Phys. Rev. B 96, 104110] Published Mon Sep 25, 2017

]]>Strain-phonon coupling, in terms of the shift in phonon frequencies under biaxial strain, is studied by density functional theory calculations for 20 perovskite oxides strained in their (111) and (001) planes. While the strain-phonon coupling under (001) strain follows the established, intuitive tre...

[Phys. Rev. B 96, 094109] Published Wed Sep 20, 2017

]]>An incommensurate phase refers to a solid state in which the period of a superstructure is incommensurable with its primitive unit cell. It was recently shown that an incommensurate phase, which displays a single chiral modulation of six domain variants, could be induced by applying an in-plane stra...

[Phys. Rev. B 96, 104109] Published Wed Sep 20, 2017

]]>High-temperature, high-dose, neutron irradiation of W results in the formation of Re-rich clusters at concentrations one order of magnitude lower than the thermodynamic solubility limit. These clusters may eventually transform into brittle W-Re intermetallic phases, which can lead to high levels of ...

[Phys. Rev. B 96, 094108] Published Mon Sep 18, 2017

]]>A density functional theory study of atomic defects and dopants in ternary Z-phase transition-metal nitrides $\mathrm{Cr}M\mathrm{N}$ with $M=\mathrm{V}$, Nb, or Ta is presented. Various defect formation energies of native point defects and of substitutional atoms of other metal elements which are abundant in the steel as well ar...

[Phys. Rev. B 96, 104107] Published Mon Sep 18, 2017

]]>Kinetic Monte Carlo simulations have been performed to investigate the evolution of ordered domains in model alloys under irradiation. The alloys investigated were equiatomic binary alloys on a simple square lattice with first and second nearest-neighbor interactions, chosen so that a $2\times 2$ ordered st...

[Phys. Rev. B 96, 104108] Published Mon Sep 18, 2017

]]>Small system sizes are a well-known source of error in density functional theory (DFT) calculations, yet computational constraints frequently dictate the use of small supercells, often as small as 96 atoms in oxides and compound semiconductors. In ionic compounds, electrostatic finite-size effects h...

[Phys. Rev. B 96, 094107] Published Fri Sep 15, 2017

]]>Our detailed temperature-dependent synchrotron powder x-ray diffraction studies along with first-principles density-functional-theory-based calculations enable us to shed light on the origin of ferroelectricity in ${\mathrm{GdCrO}}_{3}$. The actual lattice symmetry is found to be the noncentrosymmetric orthorhombic...

[Phys. Rev. B 96, 104106] Published Tue Sep 12, 2017

]]>Topological phononic states, which facilitate unique acoustic transport around defects and disorders, have significantly revolutionized our scientific cognition of acoustic systems. Here, by introducing a zone folding mechanism, we realize the topological phase transition in a double Dirac cone of t...

[Phys. Rev. B 96, 094106] Published Mon Sep 11, 2017

]]>The diffusivities of substitutional impurity elements in iron have been computed with *ab inito* electronic density functional techniques, using exchange-correlation functional PW91. Excess entropies and the attempt frequency for a jump were determined by calculating phonon frequencies in the harmonic...

[Phys. Rev. B 96, 094105] Published Thu Sep 07, 2017

]]>The authors demonstrate room-temperature multiferroic (ferroelectric-ferromagnetic) behavior in lead titanate, in which about 30% of the titanium is substituted by palladium. Palladium is an unusual element with an instability to ferromagnetism under some special conditions. Typically, it has not been easy to incorporate it into perovskite oxides – the most common structure for ferroelectric device materials. Although palladium is expensive, commercial devices like ferroelectric memories often use very thin films, for which the added cost of palladium is negligible. Thus, the present study combines basic new physics of the first multiferroic palladium compounds with potential commercial devices.

[Phys. Rev. B 96, 104104] Published Thu Sep 07, 2017

]]>The spinel $\mathrm{CoC}{\mathrm{r}}_{2}{\mathrm{O}}_{4}$ (CCO) is one of the few bulk multiferroics with net magnetic moment. However, studies on the properties of CCO thin films are scarce. Here, we investigate the interplay between microstructure and magnetism of a series of CCO epitaxial thin films by means of x-ray diffraction, magn...

[Phys. Rev. B 96, 104105] Published Thu Sep 07, 2017

]]>Shear banding is a nucleation-controlled process in metallic glasses (MGs) involving multiple temporal-spatial scales, which hinders a concrete understanding of its structural origin down to the atomic scale. Here, inspired by the morphology of composite materials, we propose a different perspective...

[Phys. Rev. B 96, 094103] Published Wed Sep 06, 2017

]]>We report high-pressure Raman experiments of black phosphorus up to 24 GPa. The linewidths of first-order Raman modes ${A}_{g}^{1},{B}_{2g}$, and ${A}_{g}^{2}$ of the orthorhombic phase show a minimum at 1.1 GPa. Our first-principles density functional analysis reveals that this is associated with the anomalies in electron...

[Phys. Rev. B 96, 094104] Published Wed Sep 06, 2017

]]>Density functional theory in principle predicts correct ground-state properties for all materials. However, the rocksalt structure of MnO has been obtained only by the high-level random phase approximation and diffusion Monte Carlo (DMC). Here, we propose and test for MnO, FeO, CoO, and NiO that a s...

[Phys. Rev. B 96, 100101(R)] Published Wed Sep 06, 2017

]]>We explore the elastic, dielectric, piezoelectric, and flexoelectric phenomenological coefficients as functions of microscopic model parameters such as ionic positions and spring constants in the two-dimensional square-lattice model with rocksalt-type ionic arrangement. Monte Carlo simulation reveal...

[Phys. Rev. B 96, 104102] Published Wed Sep 06, 2017

]]>The $\mathrm{P}{\mathrm{b}}_{\mathrm{I}}$ antisite was reported to be a possible deep-level recombination-center defect in $\mathrm{C}{\mathrm{H}}_{3}\mathrm{N}{\mathrm{H}}_{3}\mathrm{Pb}{\mathrm{I}}_{3}$ solar cells with a concentration higher than ${10}^{15}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{-3}$ under I-poor conditions. However, whether it is really an effective nonradiative recombination center and limits the photovoltaic efficiency depen...

[Phys. Rev. B 96, 104103] Published Wed Sep 06, 2017

]]>The ferroelectric to paraelectric phase transition of multiferroic ${\mathrm{CaMnTi}}_{2}{\mathrm{O}}_{6}$ has been investigated at high pressures and ambient temperature by second-harmonic generation (SHG), Raman spectroscopy, and powder and single-crystal x-ray diffraction. We have found that ${\mathrm{CaMnTi}}_{2}{\mathrm{O}}_{6}$ undergoes a pressure-ind...

[Phys. Rev. B 96, 094101] Published Tue Sep 05, 2017

]]>High-throughput first-principles calculations based on density functional theory (DFT) are a powerful tool in data-oriented materials research. The choice of approximation to the exchange-correlation functional is crucial as it strongly affects the accuracy of DFT calculations. This study compares p...

[Phys. Rev. B 96, 094102] Published Tue Sep 05, 2017

]]>The exceptional ability of carbon to form ${\mathit{sp}}^{2}$ and ${\mathit{sp}}^{3}$ bonding states leads to a great structural and chemical diversity of carbon-bearing phases at nonambient conditions. Here we use laser-heated diamond-anvil cells combined with synchrotron x-ray diffraction, Raman spectroscopy, and first-principle...

[Phys. Rev. B 96, 104101] Published Fri Sep 01, 2017

]]>A continuum/atomistic approach for predicting lattice instability during crystal-crystal phase transformations (PTs) is developed for the general loading with an arbitrary stress tensor and large strains. It is based on a synergistic combination of the generalized Landau-type theory for PTs and mole...

[Phys. Rev. B 96, 054118] Published Tue Aug 29, 2017

]]>The phonon anharmonicity in Se-doped $\mathrm{S}{\mathrm{b}}_{2}\mathrm{T}{\mathrm{e}}_{3}$ system is probed both macroscopically and microscopically using temperature-dependent synchrotron powder diffraction, Raman spectroscopic studies, and heat-capacity measurements. Gruneisen parameter (${\gamma}_{\mathrm{G}}$) is calculated to explain anharmonicity in the polycr...

[Phys. Rev. B 96, 064116] Published Tue Aug 29, 2017

]]>The phase transition evolution for ${\left[{\mathrm{KNbO}}_{3}\right]}_{1-x}{\left[{\mathrm{BaNi}}_{1/2}{\mathrm{Nb}}_{1/2}{\mathrm{O}}_{3-\delta}\right]}_{x}\phantom{\rule{0.16em}{0ex}}(x=0,0.1)$ is determined via complementary dielectric permittivity and Raman-scattering measurements. Raman scattering by optical phonons over the range of 100–$1000{\mathrm{cm}}^{-1}$ for 83 K $<T<873$ K reveals six discernible zone-center optical ...

[Phys. Rev. B 96, 054117] Published Mon Aug 28, 2017

]]>Ferroelectric perovskite oxides possess a large electrocaloric (EC) effect, but usually at high temperatures near the ferroelectric/paraelectric phase transition temperature, which limits their potential application as next-generation solid-state cooling devices. We use classical molecular dynamics ...

[Phys. Rev. B 96, 054116] Published Thu Aug 24, 2017

]]>The nucleation and growth properties of domains of molecules of the same state in open boundary three-dimensional (3D) spin-crossover systems of various shapes are discussed within the framework of the mechanoelastic model. The molecules are situated on face-centered-cubic lattices and are linked by...

[Phys. Rev. B 96, 064115] Published Thu Aug 24, 2017

]]>We present a rigorous procedure for evaluating the photoelastic coefficients of a layered medium in which the periodicity is smaller than the wavelengths of all optical and acoustic fields. Analytical expressions are given for the coefficients of a composite material comprising thin layers of optica...

[Phys. Rev. B 96, 064114] Published Wed Aug 23, 2017

]]>Ferroelectric relaxors are complex materials with distinct properties. The understanding of their dielectric susceptibility, which strongly depends on both temperature and probing frequency, has been a challenge for researchers for many years. Here we report a macroscopic and phenomenological approa...

[Phys. Rev. B 96, 054115] Published Tue Aug 22, 2017

]]>The use of proton beams in several modern technologies to probe or modify the properties of materials, such as proton beam lithography or ion beam cancer therapy, requires us to accurately know the extent to which the energy lost by the swift projectiles in the medium is redistributed radially aroun...

[Phys. Rev. B 96, 064113] Published Tue Aug 22, 2017

]]>We present simulations of Bragg coherent x-ray diffractive imaging (CXDI) data from finite crystals in the frame of the dynamical theory of x-ray diffraction. The developed approach is based on a numerical solution of modified Takagi-Taupin equations and can be applied for modeling of a broad range ...

[Phys. Rev. B 96, 064111] Published Mon Aug 21, 2017

]]>We report a systematic study of the structure, electric, and magnetic properties of ${\mathrm{Ca}}_{3}{\mathrm{Co}}_{2-x}{\mathrm{Mn}}_{x}{\mathrm{O}}_{6}$ single crystals with $x=0.72$ and 0.26. The dc and ac magnetic susceptibilities display anomalies with characteristic of the spin freezing. The crystals show ferroelectric transition at 40 and 35 K (${T}_{\mathrm{FE}}$) ...

[Phys. Rev. B 96, 064112] Published Mon Aug 21, 2017

]]>Recent progress in *extremely correlated Fermi liquid theory (ECFL)* and the *dynamical mean field theory (DMFT)* enables us to accurately compute in the $d\to \infty $ limit the resistivity of the $t-J$ model after setting $J\to 0$. This is also the $U=\infty $ Hubbard model. Since $J$ is set to zero, our study isolates the *dynam...*

[Phys. Rev. B 96, 054114] Published Fri Aug 18, 2017

]]>We use density functional theory to study intrinsic defects and oxygen related defects in indium selenide. We find that InSe is prone to oxidation, but however not reacting with oxygen as strongly as phosphorene. The dominant intrinsic defects in In-rich material are the In interstitial, a shallow d...

[Phys. Rev. B 96, 054112] Published Thu Aug 17, 2017

]]>Analysis of statistical distributions and auto- and cross correlations of polarization and electric field during the field-driven polarization reversal in a bulk polycrystalline ferroelectric is performed. A mesoscopic switching model is used which accounts self-consistently for the development of d...

[Phys. Rev. B 96, 054113] Published Thu Aug 17, 2017

]]>The crystal structure, magnetic ordering, and electrical resistivity of $\mathrm{TlF}{\mathrm{e}}_{1.6}\mathrm{S}{\mathrm{e}}_{2}$ were studied at high pressures. Below $\sim 7\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, $\mathrm{TlF}{\mathrm{e}}_{1.6}\mathrm{S}{\mathrm{e}}_{2}$ is an antiferromagnetically ordered semiconductor with a $\mathrm{ThC}{\mathrm{r}}_{2}\mathrm{S}{\mathrm{i}}_{2}$-type structure. The insulator-to-metal transformation observed at a pressure of $\sim 7\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ is accomp...

[Phys. Rev. B 96, 064109] Published Wed Aug 16, 2017

]]>The temperature-induced structural and electronic transformation in ${\mathrm{VO}}_{2}$ between the monoclinic M1 and tetragonal rutile phases was studied by means of *ab initio* molecular dynamics, based on density functional theory with Hubbard correction (DFT+$U$). We compare the structure of both phases, transition...

[Phys. Rev. B 96, 054111] Published Tue Aug 15, 2017

]]>Multidomain relaxor-based ferroelectric single crystals $\left(1\text{\u2212}x\right)\mathrm{Pb}\left(\mathrm{M}{\mathrm{g}}_{1/3}\mathrm{N}{\mathrm{b}}_{2/3}\right){\mathrm{O}}_{3}\text{\u2212}x\mathrm{PbTi}{\mathrm{O}}_{3}$ (PMN-PT) have extraordinarily large electromechanical properties, but the origin of their giant piezoelectric properties is still not well understood. The Landau-like phenomenological theory is a feasible tool to s...

[Phys. Rev. B 96, 054109] Published Mon Aug 14, 2017

]]>We study the thermal conductivity tensor in an atomistic model of vulcanized cis-1,4-polyisoprene (PI) rubber via molecular dynamics simulations. Our polymer force field is based on V. A. Harmandaris *et al.* [J. Chem. Phys. **116**, 436 (2002)], whereas the polymerization algorithm follows the descriptio...

[Phys. Rev. B 96, 054110] Published Mon Aug 14, 2017

]]>We investigate the relative stability, structural properties, and electronic structure of various modulated martensites of the magnetic shape memory alloy ${\mathrm{Mn}}_{2}\mathrm{NiGa}$ by means of density functional theory. We observe that the instability in the high-temperature cubic structure first drives the system to...

[Phys. Rev. B 96, 064107] Published Mon Aug 14, 2017

]]>We report on an extensive study of ZnO materials with cagelike motifs in clusters and bulk phases through structural searches using the minima hopping method. A novel putative ground state was discovered for the ${\left(\mathrm{ZnO}\right)}_{32}$ cluster with a tubelike structure, closely related to the previously reported ${(\mathrm{Z...}}_{}$

[Phys. Rev. B 96, 064108] Published Mon Aug 14, 2017

]]>The low-temperature behavior of tetragonal copper sulfide, ${\mathrm{Cu}}_{2}\mathrm{S}$, was investigated by powder and single-crystal x-ray diffraction, calorimetry, electrical resistance measurements, and ambient temperature optical absorption spectroscopy. The experiments were complemented by density-functional-theory-b...

[Phys. Rev. B 96, 054108] Published Fri Aug 11, 2017

]]>The quantum anomalous Hall effect, an exotic topological state first theoretically predicted by Haldane and recently experimentally observed, has attracted enormous interest for low-power-consumption electronics. In this work, we derived a Schrödinger-like equation of phonons, where topology-related...

[Phys. Rev. B 96, 064106] Published Wed Aug 09, 2017

]]>Landau theory describes phase transitions as the competition between energy and entropy: The ordered phase has lower energy, while the disordered phase has larger entropy. When heating the system, ordering is reduced entropically until it vanishes at the critical temperature. This picture implicitly...

[Phys. Rev. B 96, 054107] Published Tue Aug 08, 2017

]]>The magnetocrystalline anisotropy (MAE) of ${\mathrm{Ni}}_{2-x}{\mathrm{Pt}}_{x}\mathrm{MnGa}(0\le x\le 0.25)$ alloys are investigated using the singular point detection technique and density functional theory. A slight reduction in MAE as compared to that of ${\mathrm{Ni}}_{2}\mathrm{MnGa}$ is observed due to Pt substitution. The calculated MAE varies almost linearly...

[Phys. Rev. B 96, 054105] Published Mon Aug 07, 2017

]]>We analyze the emergence of a process zone of improper ferroelastic class. We derive expressions for the zone emergence temperature and the size of the incipient zone in terms of experimentally accessible physical parameters. Our numerical estimates suggest that the region of existence of the proces...

[Phys. Rev. B 96, 054106] Published Mon Aug 07, 2017

]]>Structural and thermoelectric properties are reported for a specially designed class of $A$-site substituted perovskite titanates, $\left(\mathrm{S}{\mathrm{r}}_{1-x-y}\mathrm{C}{\mathrm{a}}_{x}\mathrm{N}{\mathrm{d}}_{y}\right)\mathrm{Ti}{\mathrm{O}}_{3}$. Two series synthesized with various $A$-site Sr-rich or Ca-rich (Sr-poor) concentrations were investigated using high-resolution neutron powder diffract...

[Phys. Rev. B 96, 064105] Published Mon Aug 07, 2017

]]>Coherent diffraction imaging (CDI) is a rapidly developing form of imaging that offers the potential of wavelength-limited resolution without image-forming lenses. In CDI, the intensity of the diffraction pattern is measured directly by the detector, and various iterative phase retrieval algorithms ...

[Phys. Rev. B 96, 054104] Published Fri Aug 04, 2017

]]>We report a polarized Raman scattering study of nonsymmorphic topological insulator KHgSb with hourglasslike electronic dispersion. Supported by theoretical calculations, we show that the lattice of the previously assigned space group $P{6}_{3}/mmc$ (No. 194) is unstable in KHgSb. While we observe one of t...

[Phys. Rev. B 96, 064102] Published Fri Aug 04, 2017

]]>We report a comprehensive study of lattice dynamics of the Dirac node-line semimetal ZrSiS single crystal by Raman spectroscopy and first-principles calculations. The weak covalent bonding between ZrSiS layers is confirmed by the absence of low-frequency shear or breathing Raman modes down to $15\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{-1}$...

[Phys. Rev. B 96, 064103] Published Fri Aug 04, 2017

]]>We analyze and compare the structural, dynamical, and electronic properties of liquid water next to prototypical metals including Pt, graphite, and graphene. Our results are built on Born-Oppenheimer molecular dynamics (BOMD) generated using density functional theory (DFT) which explicitly include v...

[Phys. Rev. B 96, 064104] Published Fri Aug 04, 2017

]]>The force between a sharp scanning probe tip and a surface can drive a graphene flake over crystalline substrates. The recent design of particular patterns of structural defects on a graphene surface allows us to propose an alternative approach for controlling the motion of a graphene flake over a g...

[Phys. Rev. B 96, 060101(R)] Published Thu Aug 03, 2017

]]>The rotation of octahedra (octahedral tilting) is common in $AB{\mathrm{O}}_{3}$ perovskites and relevant to many physical phenomena, ranging from electronic and magnetic properties, metal-insulator transitions to improper ferroelectricity. Hydrostatic pressure is an efficient way to tune and control octahedral til...

[Phys. Rev. B 96, 054102] Published Wed Aug 02, 2017

]]>Solid-state simulations at the quantum mechanics level are mostly done by means of density functional theory (DFT). With the development of a new type of functionals about a decade ago, the accuracy of DFT for systems with relevant van der Waals interactions increased. These functionals, the so-called van der Waals functionals, have been used extensively by the pseudopotential solid-state community, but, for technical reasons, not by the community that uses all-electron methods. Here, the authors present a very simple way for the implementation of van der Waals functionals within the framework of all-electron methods. At that, the advantages of the algorithm, used in the pseudopotential methods, are preserved. The development should lead to a much more widespread use of the van der Waals functionals in the all-electron community.

[Phys. Rev. B 96, 054103] Published Wed Aug 02, 2017

]]>Low thermal polarization of nuclear spins is a primary sensitivity limitation for nuclear magnetic resonance. Here we demonstrate optically pumped (microwave-free) nuclear spin polarization of ${}^{13}\mathrm{C}$ and ${}^{15}\mathrm{N}$ in ${}^{15}\mathrm{N}$-doped diamond. ${}^{15}\mathrm{N}$ polarization enhancements up to $-2000$ above thermal equilibrium are o...

[Phys. Rev. B 96, 054101] Published Tue Aug 01, 2017

]]>Charge doping would inevitably induce strain, which can significantly influence device performance but cannot be directly predicted by classical mechanical laws. Here we present a set of equations of states for deformable cubic crystals subjected to charge doping by introducing the quantum electroni...

[Phys. Rev. B 96, 064101] Published Tue Aug 01, 2017

]]>The *in situ* x-ray pair-distribution function (PDF) characterization technique has been used to study the behavior of ${\left({\mathrm{K}}_{x}\mathrm{N}{\mathrm{a}}_{1-x}\right)}_{0.5}\mathrm{B}{\mathrm{i}}_{0.5}\mathrm{Ti}{\mathrm{O}}_{3}$, as a function of electric field. As opposed to conventional x-ray Bragg diffraction techniques, PDF is sensitive to local atomic displacements, detecting local ...

[Phys. Rev. B 96, 014118] Published Mon Jul 31, 2017

]]>Electronic, lattice, and spin interactions at the interfaces between crystalline complex transition-metal oxides can give rise to a wide range of functional electronic and magnetic phenomena not found in bulk. At heterointerfaces, these interactions may be enhanced by combining oxides where the pola...

[Phys. Rev. B 96, 024108] Published Mon Jul 31, 2017

]]>A framework for computing the anharmonic free energy (FE) of metallic crystals using Born-Oppenheimer *ab initio* molecular dynamics (AIMD) simulation, with unprecedented efficiency, is introduced and demonstrated for the hcp phase of iron at extreme conditions (up to $\approx 290$ GPa and 5000 K). The advance...

[Phys. Rev. B 96, 014117] Published Wed Jul 26, 2017

]]>$\mathrm{Ti}{\mathrm{O}}_{2}$ in the rutile phase is known to be an incipient ferroelectric. Considering Nb-Cr codoping we examine if ferroelectricity can be induced at the low doping limit in $\mathrm{T}{\mathrm{i}}_{\left(1\text{\u2212}x\right)}{\left(\mathrm{N}{\mathrm{b}}_{0.5}\mathrm{C}{\mathrm{r}}_{0.5}\right)}_{x}{\mathrm{O}}_{2}$ ($x=0.05\%$, 1%, 5%, and 10%). A relaxor behavior is found in the temperature range 20–120 K which obeys the Vog...

[Phys. Rev. B 96, 024107] Published Wed Jul 26, 2017

]]>Atomistic effective Hamiltonian simulations are used to investigate electrocaloric (EC) effects in the lead-free $\mathrm{Ba}\left({\mathrm{Zr}}_{0.5}{\mathrm{Ti}}_{0.5}\right){\mathrm{O}}_{3}$ (BZT) relaxor ferroelectric. We find that the EC coefficient varies nonmonotonically with the field at any temperature, presenting a maximum that can be traced back to th...

[Phys. Rev. B 96, 014114] Published Mon Jul 24, 2017

]]>In current fracture theory, the fracture stress is related to the surface energy on the basis of linear elastic theory. However, the fracture stress does not necessarily exceed the stress required to break atomic bonds. Here, we show that a jump in the inelastic separation energy is generated by fra...

[Phys. Rev. B 96, 014115] Published Mon Jul 24, 2017

]]>We construct a distribution function of the strain-tensor components induced by point defects in an elastically anisotropic continuum, which can be used to account quantitatively for many effects observed in different branches of condensed matter physics. Parameters of the derived six-dimensional ge...

[Phys. Rev. B 96, 014116] Published Mon Jul 24, 2017

]]>Machine-learning potentials (MLPs) for atomistic simulations are a promising alternative to conventional classical potentials. Current approaches rely on descriptors of the local atomic environment with dimensions that increase quadratically with the number of chemical species. In this paper, we dem...

[Phys. Rev. B 96, 014112] Published Fri Jul 21, 2017

]]>Although, as part of a general phenomenon, the piezoelectric response of $\mathrm{Ba}\left(\mathrm{T}{\mathrm{i}}_{1-y}{M}_{y}\right){\mathrm{O}}_{3}$ ($M=\mathrm{Zr}$, Sn, Hf) increases in the vicinity of the orthorhombic ($Amm2$)-tetragonal ($P4mm$) and orthorhombic ($Amm2$)-rhombohedral ($R3m$) polymorphic phase boundaries, experiments in the last few years have shown that the ...

[Phys. Rev. B 96, 014113] Published Fri Jul 21, 2017

]]>The self-consistent harmonic approximation is an effective harmonic theory to calculate the free energy of systems with strongly anharmonic atomic vibrations, and its stochastic implementation has proved to be an efficient method to study, from first-principles, the anharmonic properties of solids. ...

[Phys. Rev. B 96, 014111] Published Tue Jul 18, 2017

]]>Based on first-principles band-structure calculations, we predict that an inversion-breaking, stoichiometric single crystal ${\mathrm{NbIrTe}}_{4}$ is a Weyl semimetal candidate. Without spin-orbit coupling (SOC), we find that there are only eight Weyl points in the ${k}_{z}=0$ plane. The separation between Weyl points of...

[Phys. Rev. B 96, 024106] Published Tue Jul 18, 2017

]]>The properties of nanometric-sized helium bubbles in silicon have been investigated using both spatially resolved electron-energy-loss spectroscopy combined with a recently developed method, and molecular-dynamics simulations. The experiments allowed for an accurate determination of size, aspect rat...

[Phys. Rev. B 96, 014110] Published Mon Jul 17, 2017

]]>To clarify the nature of the transformation in liquid iodine, which is reported to occur at around 4 GPa, we have conducted x-ray absorption fine structure (XAFS) and x-ray diffraction (XRD) measurements up to 9 GPa. In the XAFS spectra, the oscillation attributable to the molecular bond persisted t...

[Phys. Rev. B 96, 024105] Published Mon Jul 17, 2017

]]>Bragg projection ptychography (BPP) is a coherent x-ray diffraction imaging technique which combines the strengths of scanning microscopy with the phase contrast of x-ray ptychography. Here we apply it for high resolution imaging of the phase-shifted crystalline domains associated with epitaxial gro...

[Phys. Rev. B 96, 014109] Published Fri Jul 14, 2017

]]>While high-throughput density functional theory (DFT) has become a prevalent tool for materials discovery, it is limited by the relatively large computational cost. In this paper, we explore using DFT data from high-throughput calculations to create faster, surrogate models with machine learning (ML...

[Phys. Rev. B 96, 024104] Published Fri Jul 14, 2017

]]>Based on first principles total energy calculations, we investigate geometric, electronic, and spin structures in two-dimensional polyacene-based hydrocarbon networks of $s{p}^{2}$ and $s{p}^{3}$ C atoms. Polyacenes connecting adjacent $s{p}^{3}$ atoms form kagome networks. The networks are stable and retain their coval...

[Phys. Rev. B 96, 024103] Published Thu Jul 13, 2017

]]>Cluster expansion (CE) is effective in modeling the stability of metallic alloys, but sometimes cluster expansions fail. Failures are often attributed to atomic relaxation in the DFT-calculated data, but there is no metric for quantifying the degree of relaxation. Additionally, numerical errors can ...

[Phys. Rev. B 96, 014107] Published Wed Jul 12, 2017

]]>For this paper, single-pulse ablation mechanisms of ultrafast laser pulses ($25\phantom{\rule{0.222222em}{0ex}}\mathrm{ps}$) were studied for thin gold films ($65\phantom{\rule{0.222222em}{0ex}}\mathrm{nm}$) on an array of substrates with varying physical properties. Using time-domain thermoreflectance, the interfacial properties of the thin-film systems are measured: in particular, ...

[Phys. Rev. B 96, 014108] Published Wed Jul 12, 2017

]]>We use molecular dynamics to study the vibrations of a thermally fluctuating two-dimensional elastic membrane clamped at both ends. We directly extract the eigenmodes from resonant peaks in the frequency domain of the time-dependent height and measure the dependence of the corresponding eigenfrequen...

[Phys. Rev. B 96, 014106] Published Tue Jul 11, 2017

]]>$I\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l\phantom{\rule{0.333em}{0ex}}s\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}g\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}h$ is a fundamental property describing the upper bound on a material’s strength in the absence of crystal defects. Similarly, the nature of the failure at the ideal strength can be related to the $i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}c\phantom{\rule{0.333em}{0ex}}d\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}y$ of metals and alloys. In this work, analytical expressions are derived for the ideal strength and intrinsic ductility with knowledge of only the second-order and third-order elastic constants. This analytical approach greatly improves the fundamental understanding of mechanical behavior in advanced materials.

[Phys. Rev. B 96, 014105] Published Mon Jul 10, 2017

]]>The ground state of $\mathrm{BaF}{\mathrm{e}}_{12}{\mathrm{O}}_{19}$ (BFO) is controversial as three different quantum states, namely, quantum paraelectric, frustrated antiferroelectric, and quantum electric dipole liquid (QEDL), have been proposed. We have investigated the quantum critical behavior of BFO as a function of chemical press...

[Phys. Rev. B 96, 024102] Published Mon Jul 10, 2017

]]>A nonequilibrium statistical domain nucleation model of polarization dynamics in less understood antiferroelectric systems is introduced. Predictions of the model have been successfully tested experimentally using an antiferroelectric $\mathrm{P}{\mathrm{b}}_{0.99}\mathrm{N}{\mathrm{b}}_{0.02}{\left[{\left(\mathrm{Z}{\mathrm{r}}_{0.57}\mathrm{S}{\mathrm{n}}_{0.43}\right)}_{0.94}\mathrm{T}{\mathrm{i}}_{0.06}\right]}_{0.98}{\mathrm{O}}_{3}$ polycrystalline cera...

[Phys. Rev. B 96, 014104] Published Fri Jul 07, 2017

]]>The temperature evolution of polar order in an $A$-site complex perovskite $(\mathrm{B}{\mathrm{i}}_{1/2}{\mathrm{K}}_{1/2})\mathrm{Ti}{\mathrm{O}}_{3}$ (BKT) has been investigated by measurements of dielectric permittivity, depolarization current, and stress-stain curves at elevated temperatures. Upon cooling from high temperatures, BKT first enters a relaxor s...

[Phys. Rev. B 96, 014103] Published Thu Jul 06, 2017

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