Recent research suggests that the supercritical state consists of liquidlike and gaslike states where particle dynamics and key system properties are qualitatively different. We report experimental evidence of the structural crossover in supercritical neon at pressure and temperature conditions sign…

[Phys. Rev. B 95, 134114] Published Wed Apr 26, 2017

]]>The equation of state (EOS) of carbon in its high-pressure solid and liquid phases is of interest to planetary astrophysics and inertial confinement fusion. Of particular interest are the high-pressure shock and release responses of diamond as these provide rigorous constraints on important paths th…

[Phys. Rev. B 95, 144114] Published Wed Apr 26, 2017

]]>I show that a nonequilibrium paraelectric to ferroelectric transition can be transiently induced using midinfrared pulses. This relies on a quartic $l{Q}_{{\mathrm{l}}_{z}}^{2}{Q}_{{\mathrm{h}}_{x}}^{2}$ coupling between the lowest (${Q}_{{\mathrm{l}}_{z}}$) and highest (${Q}_{{\mathrm{h}}_{x}}$) frequency infrared-active phonon modes of a paraelectric material. Density functional calc…

[Phys. Rev. B 95, 134113] Published Tue Apr 25, 2017

]]>The task of finding the smallest energy needed to bring a solid to its onset of mechanical instability arises in many problems in materials science, from the determination of the elasticity limit to the consistent assignment of free energies to mechanically unstable phases. However, unless the space…

[Phys. Rev. B 95, 144113] Published Tue Apr 25, 2017

]]>Potassium is introduced into the crystalline herringbone structure of pentacene searching for a compound showing metallic electronic transport properties and, hopefully, superconductivity at small enough temperatures. Several possible structures for stoichiometric KPentacene (1:1), ${\mathrm{K}}_{2}\mathrm{Pentacene}$ (2:1)…

[Phys. Rev. B 95, 134112] Published Mon Apr 24, 2017

]]>Observations of multiferroicity and giant improper ferroelectricity in ${\mathrm{CaMn}}_{7}{\mathrm{O}}_{12}$ invigorated the research on this material. Delicate structural changes have been reported to cause ferroelectricity in the magnetically ordered state of ${\mathrm{CaMn}}_{7}{\mathrm{O}}_{12}$ as well as high-temperature crystallographic transformatio…

[Phys. Rev. B 95, 144112] Published Mon Apr 24, 2017

]]>Plastic deformation of metallic glasses performed well below the glass transition temperature leads to the formation of shear bands as a result of shear localization. It is believed that shear banding originates from individual stress concentrators having quadrupolar symmetry. To elucidate the under…

[Phys. Rev. B 95, 134111] Published Fri Apr 21, 2017

]]>Two-dimensional crystals with strong interactions between layers has attracted increasing attention in recent years in a variety of fields. In particular, the growth of a single layer of oxide materials (e.g., MgO, CaO, NiO, and MnO) over metallic substrates were found to display different physical …

[Phys. Rev. B 95, 144109] Published Wed Apr 19, 2017

]]>The representations of a compound, called “descriptors” or “features”, play an essential role in constructing a machine-learning model of its physical properties. In this study, we adopt a procedure for generating a set of descriptors from simple elemental and structural representations. First, it i…

[Phys. Rev. B 95, 144110] Published Wed Apr 19, 2017

]]>Based on the first-principles total-energy calculation, we have studied the shear-strain gradient effect on the polarization reversal of ferroelectric ${\mathrm{BaTiO}}_{3}$ thin films. By calculating the energies of double-domain supercells for different electric polarization, shear-strain gradients, and domain-wa…

[Phys. Rev. B 95, 144111] Published Wed Apr 19, 2017

]]>We explore the stability of the ambient pressure zinc-blende polymorph (B3) structure of silicon carbide (SiC) at high pressures and temperatures where it transforms to the rocksalt (B1) structure. We find that the transition occurs ∼40 GPa lower than previously measured when heated to moderately hi…

[Phys. Rev. B 95, 134108] Published Tue Apr 18, 2017

]]>We performed a global search for possible Au-Si crystal structures using a genetic algorithm (GA) combined with density functional theory (DFT) calculations. Two Au-Si structures, $\mathrm{A}{\mathrm{u}}_{8}\mathrm{S}{\mathrm{i}}_{8}$ and $\mathrm{A}{\mathrm{u}}_{16}\mathrm{S}{\mathrm{i}}_{8}$, were found to be energetically stable and have no imaginary frequencies by phonon calculations. The …

[Phys. Rev. B 95, 134109] Published Tue Apr 18, 2017

]]>We study influence of image forces on conductance of ferroelectric tunnel junctions. We show that the influence of image forces is twofold: (i) they enhance the electroresistance effect due to polarization hysteresis in symmetric tunnel junctions at nonzero bias, and (ii) they produce the electrores…

[Phys. Rev. B 95, 134106] Published Mon Apr 17, 2017

]]>Based on the models of series and parallel connections of the two phases in a composite, analytic approximations are derived for the elastic constants (Young's modulus, shear modulus, and Poisson's ratio) of elastically isotropic two-phase composites containing second phases of various volume fracti…

[Phys. Rev. B 95, 134107] Published Mon Apr 17, 2017

]]>MoAlB is the first and, so far, the only transition-metal boride that forms alumina when heated in air and is thus potentially useful for high-temperature applications. Herein, the thermal stability in argon and vacuum atmospheres and the thermodynamic parameters of bulk polycrystalline MoAlB were i…

[Phys. Rev. B 95, 144108] Published Thu Apr 13, 2017

]]>High-pressure x-ray diffraction measurements have been carried out on the intermetallic semiconductor ${\mathrm{FeGa}}_{3}$ and the equation of state for ${\mathrm{FeGa}}_{3}$ has been determined. First-principles based DFT calculations within the GGA approximation indicate that although the unit cell volume matches well with the …

[Phys. Rev. B 95, 134105] Published Wed Apr 12, 2017

]]>We use a continuum method informed by transport coefficients computed using self-consistent mean field theory to model vacancy-mediated diffusion of substitutional Si solutes in FCC Ni near an $\frac{a}{2}\left[1\overline{1}0\right]\left(111\right)$ edge dislocation. We perform two sequential simulations: first under equilibrium boundary con…

[Phys. Rev. B 95, 144107] Published Tue Apr 11, 2017

]]>Twin growth in hexagonal close-packed zirconium is investigated at the atomic scale by modeling the various disconnections that can exist on twin boundaries. Thanks to a coupling with elasticity theory, core energies are extracted from atomistic simulations, and the formation energy of isolated disc…

[Phys. Rev. B 95, 134102] Published Mon Apr 10, 2017

]]>The absorption peaks at $\sim 3200-3300\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{-1}$ in $\alpha \text{\u2212}\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$ crystal that were previously observed and assigned to hydrogen interstitial were reinvestigated by first-principles local vibration mode calculations. Based on our calculations, we found that the vibration of hydrogen interstitial is not consistent w…

[Phys. Rev. B 95, 134103] Published Mon Apr 10, 2017

]]>We study the nonequilibrium dynamics of second-order classical phase transitions in a simplified Ginzburg-Landau model using the Fokker-Planck formalism. In particular, we focus on deriving the Kibble-Zurek scaling laws that dictate the dependence of spatial correlations on the quench rate. In the l…

[Phys. Rev. B 95, 134104] Published Mon Apr 10, 2017

]]>Synchrotron x-ray diffraction and Raman spectroscopy have been used to study the chemical reactions of molecular hydrogen $\left({\mathrm{H}}_{2}\right)$ with sulfur (S) at high pressures. We find theoretically predicted *Cccm* and $Im\overline{3}m$ ${\mathrm{H}}_{3}\mathrm{S}$ to be the reaction products at 50 and 140 GPa, respectively. $Im\overline{3}m$ ${\mathrm{H}}_{3}\mathrm{S}$ is a stable crys…

[Phys. Rev. B 95, 140101(R)] Published Mon Apr 10, 2017

]]>The structural and electronic properties of $\mathrm{BaC}{\mathrm{r}}_{2}\mathrm{A}{\mathrm{s}}_{2}$, which is isostructural to the 122 iron arsenide superconductors, are studied at high pressures using synchrotron x-ray powder diffraction, electrical resistivity measurements, and first-principles calculations. At a pressure of about 18.5 GPa, an…

[Phys. Rev. B 95, 144106] Published Fri Apr 07, 2017

]]>Water and ammonia have long been seen as the main species of extraterrestrial space, especially on solar giants, moons, comets, and numerous extrasolar planets. The phases formed by their admixtures under temperature and pressure conditions of the giant planets are important for understanding many o…

[Phys. Rev. B 95, 144104] Published Thu Apr 06, 2017

]]>We present molecular dynamics simulations based on finite-temperature density functional theory that determine self-consistently the dynamic ion structure factor and the electronic form factor in lithium. Our comprehensive data set allows for the calculation of the dispersion relation for collective…

[Phys. Rev. B 95, 144105] Published Thu Apr 06, 2017

]]>Evidence in support of a shear driven anomaly in zirconium at elevated temperatures and pressures has been determined through the combined use of ultrasonic, diffractive, and radiographic techniques. Implications that these have on the phase diagram are explored through thermoacoustic parameters ass…

[Phys. Rev. B 95, 134101] Published Wed Apr 05, 2017

]]>A thorough structural exploration has been made on the quasi-one-dimensional $S=1/2$ compound $\mathrm{L}{\mathrm{i}}_{2}\mathrm{C}{\mathrm{u}}_{2}\mathrm{O}{\left(\mathrm{S}{\mathrm{O}}_{4}\right)}_{2}$ by neutron and synchrotron x-ray diffraction. It reveals the occurrence of a structural transition at 125 K, characterized by a lowering of symmetry from $P{4}_{2}/m$ to $P\overline{1}$, which is possibly driven b…

[Phys. Rev. B 95, 144103] Published Wed Apr 05, 2017

]]>Crystal structure prediction methods and first-principles calculations have been used to explore low-energy structures of carbon monoxide (CO). Contrary to the standard wisdom, the most stable structure of CO at ambient pressure was found to be a polymeric structure of $Pna{2}_{1}$ symmetry rather than a m…

[Phys. Rev. B 95, 144102] Published Tue Apr 04, 2017

]]>We report that the lowest energy transverse-optic phonon in metallic SnTe softens to near zero energy at the structural transition at ${T}_{C}=75\phantom{\rule{4.pt}{0ex}}\text{K}$ and importantly show that the energy of this mode below ${T}_{C}$ increases as the temperature decreases. Since the mode is a polar displacement this proves unambiguo…

[Phys. Rev. B 95, 144101] Published Mon Apr 03, 2017

]]>Computer simulations show that a uniform but not periodic arrangement of tiny, wave-scattering pillars can host an efficient acoustic channel of arbitrary shape.

[Phys. Rev. B 95, 094120] Published Fri Mar 31, 2017

]]>The formation of monolayer and multilayer ice with a square lattice structure has recently been reported on the basis of transmission electron microscopy experiments, renewing interest in confined two-dimensional ice. Here we report a systematic density functional theory study of double-layer ice in…

[Phys. Rev. B 95, 094121] Published Fri Mar 31, 2017

]]>Ubiquitous on Earth, *α*-quartz plays an important role in modern science and technology. However, despite extensive research in the past, the mechanism of the polymorphic transitions of *α*-quartz at high pressures remains poorly understood. Here, combining *in situ* single-crystal x-ray diffraction expe…

[Phys. Rev. B 95, 104112] Published Fri Mar 31, 2017

]]>We report a paradigm of ferrielectricity in a single-phase crystal, tris-sarcosine calcium chloride [TSCC; ${\left(\mathrm{C}{\mathrm{H}}_{3}\mathrm{NHC}{\mathrm{H}}_{2}\mathrm{COOH}\right)}_{3}\mathrm{CaC}{\mathrm{l}}_{2}]$. Ferrielectricity is well known in smectic liquid crystals but almost unknown in true crystalline solids. C. F. Pulvari [Ferrielectricity, Phys. Rev. **120**, 1670 (1960)] rep…

[Phys. Rev. B 95, 094119] Published Tue Mar 28, 2017

]]>Transition-metal dichalcogenide $\mathrm{IrT}{\mathrm{e}}_{2}$ has attracted attention because of its striped lattice, charge ordering, and superconductivity. We have investigated the surface structure of $\mathrm{IrT}{\mathrm{e}}_{2}$, using low-energy electron diffraction and scanning tunneling microscopy. A complex striped lattice modulation as …

[Phys. Rev. B 95, 094118] Published Fri Mar 24, 2017

]]>We studied the Nb-H system over extended pressure and temperature ranges to establish the highest level of hydrogen abundance we could achieve from the resulting alloy. We probed the Nb-H system with laser heating and x-ray diffraction complemented by numerical density functional theory-based simula…

[Phys. Rev. B 95, 104110] Published Fri Mar 24, 2017

]]>Modern integrated circuits (ICs) employ a myriad of materials organized at nanoscale dimensions, and certain critical tolerances must be met for them to function. To understand departures from intended functionality, it is essential to examine ICs as manufactured so as to adjust design rules ideally…

[Phys. Rev. B 95, 104111] Published Fri Mar 24, 2017

]]>Uranium nitride fuel is considered for fast reactors (GEN-IV generation and space reactors) and for light water reactors as a high-density fuel option. Despite this large interest, there is a lack of information about its behavior for in-pile and out-of-pile conditions. From the present literature, …

[Phys. Rev. B 95, 094117] Published Thu Mar 23, 2017

]]>Carbides play a central role for the strength and ductility in many materials. Simulating the impact of these precipitates on the mechanical performance requires knowledge about their atomic configuration. In particular, the C content is often observed to substantially deviate from the ideal stoichi…

[Phys. Rev. B 95, 104108] Published Wed Mar 22, 2017

]]>Thermally fluctuating sheets and ribbons provide an intriguing forum in which to investigate strong violations of Hooke's Law: Large distance elastic parameters are in fact not constant but instead depend on the macroscopic dimensions. Inspired by recent experiments on free-standing graphene cantile…

[Phys. Rev. B 95, 104109] Published Wed Mar 22, 2017

]]>We present the results of exact numerical calculations of the dielectric properties of tetrathiafulvalene-$p$-chloranil (TTF-CA) using the extended Hubbard model. The electronic polarization ${\overline{P}}_{\mathrm{el}}$ of the ionic ground state is obtained by directly calculating the adiabatic flow of current. The direction…

[Phys. Rev. B 95, 094116] Published Mon Mar 20, 2017

]]>The friction behavior of atomically stepped metal surfaces under contact loading is studied using molecular dynamics simulations. While real rough metal surfaces involve roughness at multiple length scales, the focus of this paper is on understanding friction of the smallest scale of roughness: atom…

[Phys. Rev. B 95, 104106] Published Mon Mar 20, 2017

]]>The dynamics of the phase separation of very dilute ${}^{3}$He-${}^{4}$He solid solutions is studied using high-sensitivity low-temperature NMR techniques. This paper compares the results observed at very low concentrations (down to 16 ppm ${}^{3}$He) with previous results up to 2%. The growth of ${}^{3}$He nanodroplets after phase separation is analyzed and shown to follow a one-third power-law dependence at long times as expected for Ostwald ripening. The time scale for the dynamics is governed by the relatively fast quantum diffusion in solid helium, allowing the long-term behavior of the ripening process to be explored by experiments lasting a few days rather than several months, as in the case of metallic alloys.

[Phys. Rev. B 95, 104107] Published Mon Mar 20, 2017

]]>We start from the polynomial interatomic potentials introduced by Wojdeł *et al.* [J. Phys.: Condens. Matter **25**, 305401 (2013)] and take advantage of one of their key features—namely, the linear dependence of the energy on the potential's adjustable parameters—to devise a scheme for the construction o…

[Phys. Rev. B 95, 094115] Published Thu Mar 16, 2017

]]>We investigate the accuracy and transferability of a recently developed high-dimensional neural network (NN) method for calcium fluoride, fitted to a database of *ab initio* density functional theory (DFT) calculations based on the Perdew-Burke-Ernzerhof (PBE) exchange correlation functional. We call …

[Phys. Rev. B 95, 104105] Published Thu Mar 16, 2017

]]>We studied isotopically enriched nano- and microdiamonds with optically active ${\mathrm{GeV}}^{-}$ centers synthesized at high pressures and high temperatures in nonmetallic growth systems. The influence of isotopic composition on optical properties has been thoroughly investigated by photoluminescence-excitation …

[Phys. Rev. B 95, 094113] Published Wed Mar 15, 2017

]]>We address the impact of tantalum alloying on dislocation properties of tungsten. To that aim, we calculate elastic constants, atomic-row displacement energy, dislocation core energy, and Peierls stress for different degrees of alloying within the framework of density-functional theory. We show that…

[Phys. Rev. B 95, 094114] Published Wed Mar 15, 2017

]]>Elastic strain is potentially an important approach in tuning the properties of the improperly multiferroic hexagonal ferrites, the details of which, however, have been elusive due to experimental difficulties. Employing the method of restrained thermal expansion, we have studied the effect of isoth…

[Phys. Rev. B 95, 094110] Published Tue Mar 14, 2017

]]>The dielectric function of several amorphous phase-change materials has been determined by employing a combination of impedance spectroscopy (9 kHz–3 GHz) and optical spectroscopy from the far- $(20\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{-1}$, 0.6 THz) to the near- $(12\phantom{\rule{0.16em}{0ex}}000\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{-1}$, 360 THz) infrared, i.e., from the DC limit to the first interba…

[Phys. Rev. B 95, 094111] Published Tue Mar 14, 2017

]]>Generalized stacking fault energies of nondilute binary alloys in the Ag-Au-Pd system are calculated using density functional theory and special quasirandom structures. Supercells containing 90 and 135 atoms are compared for direct calculations of the generalized stacking fault energy, and the axial…

[Phys. Rev. B 95, 094112] Published Tue Mar 14, 2017

]]>A first-principles-based effective Hamiltonian technique is used to investigate the polarization switching mechanisms in two polymorphic phases of ${\mathrm{BiFeO}}_{3}$ having no defects. The switching mechanism is homogeneous for any switching field in the rhombohedral phase, while in the supertetragonal phase it…

[Phys. Rev. B 95, 104104] Published Tue Mar 14, 2017

]]>We describe a classical thermodynamic model that reproduces the main features of the solid hydrogen phase diagram. In particular, we show how the general structure types, which are found by electronic structure calculations and the quantum nature of the protons, can also be understood from a classic…

[Phys. Rev. B 95, 094107] Published Mon Mar 13, 2017

]]>We show that single-crystal, equiatomic solid solutions of Lennard-Jones particles have a plurality of inherent states: mechanically stable configurations with identical lattice site occupancies, yet distinct potential-energy minima. External loading triggers transitions between inherent states via …

[Phys. Rev. B 95, 094108] Published Mon Mar 13, 2017

]]>This work discloses a surprising, previously unknown heterogeneous growth mode. Namely, large-area, thin sheets of *single-crystalline* Ge were observed to grow laterally on top of a *polycrystalline* Al substrate, covering as many as tens of differently oriented Al grains at low temperatures. The obser…

[Phys. Rev. B 95, 094109] Published Mon Mar 13, 2017

]]>This work explores the Zn vacancy in ZnO using hybrid density functional theory calculations. The Zn vacancy is predicted to be an exceedingly deep polaronic acceptor that can bind a localized hole on each of the four nearest-neighbor O ions. The hole localization is accompanied by a distinct outwar…

[Phys. Rev. B 95, 094105] Published Fri Mar 10, 2017

]]>We consider in detail a simple model supporting a single floppy mode that is often used to heuristically describe instances of negative thermal expansion. A key result is that the translational kinetic energy of the dilating bond network scales extensively with system size and results in dynamical p…

[Phys. Rev. B 95, 094106] Published Fri Mar 10, 2017

]]>Charged domain walls (CDWs), which possess metallic-type conductivity and can be created and controlled in the bulk of wide-band-gap ferroelectrics, attract nowadays a strong research interest. The most advanced method for production of stable CDWs involves weak super-band-gap illumination. Here, we…

[Phys. Rev. B 95, 104102] Published Fri Mar 10, 2017

]]>Positron annihilation spectroscopy characterization results for neutron-irradiated $3C$-SiC are described here, with a specific focus on explaining the size and character of vacancy clusters as a complement to the current understanding of the neutron irradiation response of $3C$-SiC. Positron annihilati…

[Phys. Rev. B 95, 104103] Published Fri Mar 10, 2017

]]>Ferroelectrics usually adopt a multidomain state with domain walls separating domains with polarization axes oriented differently. It has long been recognized that domain walls can dramatically impact the properties of ferroelectric materials. The enhancement of low-field susceptibility/permittivity…

[Phys. Rev. B 95, 094102] Published Wed Mar 08, 2017

]]>Modeling the dislocation glide through atomic-scale simulations in pure solids and alloys, the authors show that in the course of the plastic deformation the variation of the crystal’s zero point energy (ZPE) and the dislocation potential energy barriers are of opposite sign. The multiplicity of situations in which this same trend has been observed allows us to conclude that quantum fluctuations, giving rise to crystal ZPE, make dislocation glide easier in most materials.

[Phys. Rev. B 95, 094103] Published Wed Mar 08, 2017

]]>The anharmonic effect in thermoelectrics has been a central topic for decades in both condensed matter physics and material science. However, despite the long-believed strong and complex anharmonicity in the ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3-x}{\mathrm{Se}}_{x}$ series, experimental verification of anharmonicity and its evolution with doping…

[Phys. Rev. B 95, 094104] Published Wed Mar 08, 2017

]]>Using first principles density functional theory calculations combined with quasi-harmonic approximation, we demonstrate that the recently reported nonsymmorphic “hourglass fermion” materials $\text{KHg}X$ $(X=\mathrm{As}$, Sb) belong to a type of negative thermal expansion (NTE) material with an abnormal volumetric th…

[Phys. Rev. B 95, 104101] Published Wed Mar 08, 2017

]]>The proposal of sliding phases (SP) is revisited from the perspective of duality. A generic argument is formulated as essentially a no-go theorem for SP in translationally invariant nonfrustrated systems with short-range interactions—classical or quantum. Its validity is demonstrated on an asymmetri…

[Phys. Rev. B 95, 094101] Published Mon Mar 06, 2017

]]>Searching for ultrahard materials is of great interest in scientific research and for industrial applications. Boron carbide $\left({\mathrm{B}}_{4}\mathrm{C}\right)$ is one of the hardest known materials, but its Vickers hardness (30 GPa) is much less than diamond (115 GPa) and cubic boron nitride (48 GPa). A new ${\mathrm{B}}_{4}\mathrm{C}$ phase with twinl…

[Phys. Rev. B 95, 100101(R)] Published Fri Mar 03, 2017

]]>Thin amorphous bands are often thought to be the cause of drastic change of properties in boron-based ceramics. We investigate possible mechanisms of amorphization by performing a large-scale molecular dynamics study of defect formation in $\alpha $-boron. Activation of the [101]/(010) slipping system leads…

[Phys. Rev. B 95, 064113] Published Tue Feb 28, 2017

]]>Standard Landau theory coupled to infinitesimal strain allows a concise description of the temperature-driven ferroelectric tetragonal-to-cubic phase transition in ${\mathrm{PbTiO}}_{3}$ at ambient pressure. Unfortunately, it fails to cover its high-pressure counterpart at ambient temperature. For example, the expe…

[Phys. Rev. B 95, 064111] Published Mon Feb 27, 2017

]]>The quality of kinetic Monte Carlo (KMC) simulations of microstructure evolution in alloys relies on the parametrization of point-defect migration rates, which are complex functions of the local chemical composition and can be calculated accurately with *ab initio* methods. However, constructing relia…

[Phys. Rev. B 95, 064112] Published Mon Feb 27, 2017

]]>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

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