Simultaneous time-and-space resolved reflectivity and interferometric measurements over a temporal span of 300 ps have been performed in fused silica and sapphire samples excited with 800 nm, 120 fs laser pulses at energies slightly and well above the ablation threshold. The experimental results hav...

[Phys. Rev. B 95, 214114] Published Tue Jun 27, 2017

]]>Taking pure Mg, Mg-Al, and Mg-Zn as prototypes, the effects of strain on the stacking fault energies (SFEs), dislocation core structure, and Peierls stress were systematically investigated by means of density functional theory and the semidiscrete variational Peierls-Nabarro model. Our results sugge...

[Phys. Rev. B 95, 224106] Published Thu Jun 22, 2017

]]>The coherent high-fidelity generation of nuclear spins in long-lived singlet states, which may find application as quantum memory or sensor, represents a considerable experimental challenge. Here, we propose a dissipative scheme that achieves the preparation of pairs of nuclear spins in long-lived s...

[Phys. Rev. B 95, 224105] Published Wed Jun 21, 2017

]]>We study dissipation in palladium (Pd) nanomechanical resonators at low temperatures in the linear response regime. Metallic resonators have shown characteristic features of dissipation due to tunneling two-level systems (TLS). The system described here offers a unique tunability of the dissipation ...

[Phys. Rev. B 95, 214113] Published Tue Jun 20, 2017

]]>Multiple reverberation compression can achieve higher pressure, higher temperature, but lower entropy. It is available to provide an important validation for the elaborate and wider planetary models and simulate the inertial confinement fusion capsule implosion process. In the work, we have develope...

[Phys. Rev. B 95, 224104] Published Tue Jun 20, 2017

]]>We perform oscillatory shear simulations to determine the loss modulus for three solids with identical interaction yet distinct structures: ordered, random, and glassy alloys. Random and glassy alloys show more pronounced high-frequency loss in the THz regime than the ordered alloy. Ordered and rand...

[Phys. Rev. B 95, 214112] Published Mon Jun 19, 2017

]]>Infrared reflectance spectra of the polar optic phonons in a ${[{\left({\mathrm{BaTiO}}_{3}\right)}_{8}/{\left({\mathrm{SrTiO}}_{3}\right)}_{4}]}_{50}$ superlattice over the temperature range 8 to 650 K are reported. The spectra exhibit lattice vibration features typical of the perovskite constituents, ${\mathrm{BaTiO}}_{3}$ and ${\mathrm{SrTiO}}_{3}$. Using the effective medium approximation for...

[Phys. Rev. B 95, 214110] Published Thu Jun 15, 2017

]]>The prediction for the stability of glassy material is a key challenge in physical science. Here, we report a theoretical framework to predict the glass stability based on stochastic surface walking global optimization and reaction pathway sampling. This is demonstrated by revealing for the first ti...

[Phys. Rev. B 95, 214111] Published Thu Jun 15, 2017

]]>Palladium normally does not easily substitute for Ti or Zr in perovskite oxides. Moreover, Pd is not normally magnetic (but becomes ferromagnetic under applied uniaxial stress or electric fields). Despite these two great obstacles, we have succeeded in fabricating lead zirconate titanate with 30% Pd...

[Phys. Rev. B 95, 214109] Published Wed Jun 14, 2017

]]>Substitutional solutes in metals generally diffuse by successive exchanges with vacancies, that is, via the so called vacancy mechanism. However, recent density functional theory (DFT) calculations predicted an atypical behavior for the oversized solute atoms (OSAs) in bcc and fcc iron. These solute...

[Phys. Rev. B 95, 214108] Published Mon Jun 12, 2017

]]>An optimized interatomic potential has been constructed for silicon using a modified Tersoff model. The potential reproduces a wide range of properties of Si and improves over existing potentials with respect to point defect structures and energies, surface energies and reconstructions, thermal expa...

[Phys. Rev. B 95, 224103] Published Mon Jun 12, 2017

]]>We present a novel energetic model that takes into account atomistic relaxations to describe the thermodynamic properties of ${A}_{c}{B}_{1-c}$ binary alloys. It requires the calculation of the energies on each site of a random solid solution after relaxation as a function of both the local composition and the ...

[Phys. Rev. B 95, 224102] Published Thu Jun 08, 2017

]]>The recent discovery of shape memory behavior in Mg-Sc alloys has opened the door to the possibility of lightweight shape memory alloys. Very little is known, however, about martensitic phase transformations or about equilibrium phase stability in this alloy system. Here we report on a first-princip...

[Phys. Rev. B 95, 214107] Published Tue Jun 06, 2017

]]>Weyl semimetals are materials with topological defects in their band structure. They arise through mechanisms similar to vortex–anti-vortex pair creation, forming a hedgehog-structure in momentum space that is described by a four-dimensional energy-momentum Dirac cone. The authors show that, under pressure, the Dirac cone can be tilted in the same way as the relativistic light cone is tilted on approach to the black hole horizon. Following through with this analogy, at the defined horizon, time and space reversal may trigger unconventional phenomena, including the possibility for time travel. For Weyl semimetals under pressure, this means the creation of a new topological hyperbolic phase, which is anisotropic and highly active to electromagnetic radiation. Electrons may propagate across a multilayer structure made of Weyl semimetals analogous to light. Such a multilayer sandwich may have a negative refractive index for electron waves and, therefore, it may act as an electron-focusing Veselago lens. In this case, it would become possible to confine electrons to an extremely narrow beam. In the context of applications, this effect could be used to improve the resolution of the scanning electron microscopy technique, by constructing tunneling tips made up of Weyl semimetal multilayers.

[Phys. Rev. B 95, 214103] Published Mon Jun 05, 2017

]]>The elasticity at high pressure of solid hydrogen in hexagonal close-packed (hcp) phase I has been examined experimentally by laser acoustics technique in a diamond anvil cell, up to 55 GPa at 296 K, and theoretically using pair and three-body semiempirical potentials, up to 160 GPa. In the experime...

[Phys. Rev. B 95, 214104] Published Mon Jun 05, 2017

]]>Based on simultaneous force and conductance simulations, a proof of concept for a potential method of molecular detection is presented. Using density functional theory calculations, a metallic tip has been approached to different small inorganic molecules such as CO, ${\mathrm{CO}}_{2}$, ${\mathrm{H}}_{2}\mathrm{O}$, NO, ${\mathrm{N}}_{2}$, or ${\mathrm{O}}_{2}$. The mol...

[Phys. Rev. B 95, 214105] Published Mon Jun 05, 2017

]]>We investigated the local structure deformation induced by x-ray irradiation in an organic molecular conductor $\kappa -{\left(\mathrm{BEDT}-\mathrm{TTF}\right)}_{2}\mathrm{Cu}\left[\mathrm{N}{\left(\mathrm{CN}\right)}_{2}\right]\mathrm{Br}$ using density-functional-theory (DFT-) based first-principles calculations. Our results demonstrate that the structure change due to x-ray excitation can be predic...

[Phys. Rev. B 95, 214106] Published Mon Jun 05, 2017

]]>The spin relaxation in chromium spinel oxides $A{\mathrm{Cr}}_{2}{\mathrm{O}}_{4}$ ($A=$ Mg, Zn, Cd) is investigated in the paramagnetic regime by electron spin resonance (ESR). The temperature dependence of the ESR linewidth indicates an unconventional spin-relaxation behavior, similar to spin-spin relaxation in the two-dimension...

[Phys. Rev. B 95, 224101] Published Mon Jun 05, 2017

]]>Materials with the morphotropic phase boundary (MPB) exhibit an ultrahigh mechanical response to electrical inputs, which has been widely used in applications such as sensors and actuators. Recently, the rare-earth element doped $\mathrm{BiFe}{\mathrm{O}}_{3}$ (BFO) was found to possess a MPB between a rhombohedral polar ph...

[Phys. Rev. B 95, 214101] Published Thu Jun 01, 2017

]]>The enthalpy of formation is an important thermodynamic property. Developing fast and accurate methods for its prediction is of practical interest in a variety of applications. Material informatics techniques based on machine learning have recently been introduced in the literature as an inexpensive...

[Phys. Rev. B 95, 214102] Published Thu Jun 01, 2017

]]>Density functional theory calculations using the quasiharmonic approximation have been used to calculate the solid Hugoniot of two polytypes of boron carbide up to 100 GPa. Under the assumption that segregation into the elemental phases occurs around the pressure that the ${\mathrm{B}}_{11}{\mathrm{C}}_{\text{p}}$(CBC) polytype becomes...

[Phys. Rev. B 95, 184111] Published Wed May 31, 2017

]]>The magnetoelectric coupling, a phenomenon inducing magnetic (electric) polarization by application of an external electric (magnetic) field and first conjectured by Curie in 1894, is observed in most of the multiferroics and used for many applications in various fields such as data storage or sensi...

[Phys. Rev. B 95, 184112] Published Wed May 31, 2017

]]>Orbital degrees of freedom are a key ingredient in unconventional physics, including colossal magnetoresistance (CMR). When ordered, orbital arrangements can be characterized using conventional crystallographic approaches. Yet CMR emerges from states of orbital disorder, for which the experimental signature is much more ambiguous. Here, the authors study the CMR parent compound LaMnO${}_{3}$, using total scattering to understand its orbital order/disorder transition. They find a discontinuous change in local structure that indicates a fundamental change in the type of orbital arrangement at the transition. The analysis highlights the difficulty of discriminating between local structural models when static and dynamic disorder are strongly coupled.

[Phys. Rev. B 95, 174107] Published Tue May 30, 2017

]]>We have investigated magnetic and ferroelectric (dielectric) properties of multiferroic ${\mathrm{CuFe}}_{0.982}{\mathrm{Ga}}_{0.018}{\mathrm{O}}_{2},{\mathrm{CuFe}}_{0.965}{\mathrm{Ga}}_{0.035}{\mathrm{O}}_{2}$, and ${\mathrm{CuFe}}_{0.95}{\mathrm{Al}}_{0.05}{\mathrm{O}}_{2}$ under applied uniaxial pressure $p$ up to 600 MPa. Unlike the results of the almost same experiments on ${\mathrm{CuFeO}}_{2}$ [Tamatsukuri *et al.*, Phys. Rev. B **94**, 174...

[Phys. Rev. B 95, 174108] Published Tue May 30, 2017

]]>Neutron single-crystal diffraction and rotational anisotropy optical second harmonic generation data are presented resolving the nature of the structural distortion realized in electron-doped (${\mathrm{Sr}}_{1-x}{\mathrm{La}}_{x}$)${}_{3}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$ with $x=0.035$ and $x=0.071$. Once electrons are introduced into the bilayer spin-orbit assiste...

[Phys. Rev. B 95, 174109] Published Tue May 30, 2017

]]>The structural properties, energetics, and polarizations of perovskite-based thin-film oxide systems are computed as a function of biaxial strain state and epitaxial orientation, employing an automated computational workflow based on density functional theory. A total of 14 compositions are consider...

[Phys. Rev. B 95, 174110] Published Tue May 30, 2017

]]>The compression behavior of deuterated ice VII and VIII was investigated by high pressure neutron scattering in the pressure range 2–13.7 GPa between 93 and 300 K. We establish equations of state which contain accurate values for the bulk moduli ${B}_{0}$, their pressure derivatives ${B}_{0}^{\prime}$, as well as the amb...

[Phys. Rev. B 95, 174111] Published Tue May 30, 2017

]]>Defect motion in solid helium has a unique quantum nature due to the large zero-point motion of helium atoms, which allows vacancies and isotopic impurities to tunnel and move ballistically. Recent shear modulus experiments showed that dislocations are also extraordinarily mobile in solid ${}^{4}\mathrm{He}$. The l...

[Phys. Rev. B 95, 180103(R)] Published Tue May 30, 2017

]]>The application of transformation theory to underwater acoustics has been a challenging task because highly anisotropic density is unachievable in water. A possible strategy is to exploit the anisotropic modulus rather than density, although it has not been experimentally demonstrated. We present an...

[Phys. Rev. B 95, 180104(R)] Published Tue May 30, 2017

]]>We propose an approach to perform the global search for low-lying crystal structures from first principles, by combining the artificial force induced reaction (AFIR) method and the periodic boundary conditions (PBCs). The AFIR method has been applied extensively to molecular systems to elucidate the...

[Phys. Rev. B 95, 184110] Published Tue May 30, 2017

]]>Classical molecular dynamics calculations were used to investigate the formation of defects produced during irradiation of energetic ions on silicon. The aim of this study was to characterize the nature of defects and defective regions formed through ion irradiation and to establish a connection bet...

[Phys. Rev. B 95, 184109] Published Wed May 24, 2017

]]>As one of the most common waves in daily life, scalar sound is not easy to control by external fields since it lacks the intrinsic degrees of freedom such as the charge and spin in electrons. Here, the authors present an experimental observation of acoustic vortex states in sonic crystals, where the vortex chirality forms a good carrier of information for sound. By selectively exciting such novel states, they have fabricated a lattice array of sound vortices, and controlled the vortex chirality according to the operating frequency or incident direction of external sound. Furthermore, a peculiar beam-splitting behavior is observed, where the two spatially separated sound beams carry opposite vortex chirality, as manifested in the image here.

[Phys. Rev. B 95, 174106] Published Tue May 23, 2017

]]>We demonstrate that the strain of an epitaxially grown film, which is induced by the lattice mismatch between the crystalline substrate and film and relaxes with increasing film thickness, can be conserved beyond the critical thickness of plastic relaxation of the respective film/substrate heterostr...

[Phys. Rev. B 95, 184108] Published Tue May 23, 2017

]]>It is known that the orbital disordered orthorhombic ($Pnma$) perovskite, $\mathrm{YV}{\mathrm{O}}_{3}$, undergoes a transition to the $G$-type orbital ordered monoclinic phase $(P{112}_{1}/a)$ at ${T}_{G-\mathrm{OO}}\sim 200\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ followed by a first-order transition to the $C$-type orbital ordered orthorhombic phase ($Pnma$) at ${T}_{S}\sim 77\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. In contrast, using the h...

[Phys. Rev. B 95, 184107] Published Fri May 19, 2017

]]>The optical absorption of ${\mathrm{CdWO}}_{4}$ is reported at high pressures up to 23 GPa. The onset of a phase transition was detected at 19.5 GPa, in good agreement with a previous Raman spectroscopy study. The crystal structure of the high-pressure phase of ${\mathrm{CdWO}}_{4}$ was solved at 22 GPa, employing single-crystal s...

[Phys. Rev. B 95, 174105] Published Thu May 18, 2017

]]>With the aim of manipulating the mechanical properties of the recently discussed two-dimensional material MXene, we investigate the effect of alloying. We consider substitutional doping of B and V at Ti and C sites of ${\mathrm{Ti}}_{2}\mathrm{C}$. Calculations of quantities such as in-plane stiffness, Young's modulus, and ...

[Phys. Rev. B 95, 184106] Published Thu May 18, 2017

]]>Understanding how surrounding environments act on the functional properties of switchable nano-objects across extended and multiple length scales is of growing interest in many areas of material science. Here, we examine in details, using a microscopic model, the interplay between the structural pro...

[Phys. Rev. B 95, 174104] Published Tue May 16, 2017

]]>Theoretical predictions of pressure-induced phase transformations often become long-standing enigmas because of limitations of contemporary available experimental possibilities. Hitherto the existence of a nonicosahedral boron allotrope has been one of them. Here we report on a nonicosahedral boron ...

[Phys. Rev. B 95, 180102(R)] Published Tue May 16, 2017

]]>The structural phase transition in hexagonal ${\mathrm{BaMnO}}_{3}$ occurring at ${T}_{\mathrm{C}}=130$ K was studied in ceramic samples using electron and x-ray diffraction, second harmonic generation, as well as by dielectric and lattice dynamic spectroscopies. The low-temperature phase (space group $P{6}_{3}cm)$ is ferroelectric with ...

[Phys. Rev. B 95, 174103] Published Fri May 12, 2017

]]>We develop a multiscale approach to quantify the increase in the recombined fraction of point defects under irradiation resulting from dilute solute additions to a solid solution. This methodology provides design principles for radiation-resistant materials. Using an existing database of solute diff...

[Phys. Rev. B 95, 174102] Published Wed May 10, 2017

]]>We investigate the evolution of large number of ${\delta}^{\prime}$ coherent precipitates from a supersaturated Al-8 at.% Li alloy using large-scale phase-field simulations. A chemomechanical cross-coupling between mechanical relaxation and diffusion is taken into account by considering the dependence of elastic con...

[Phys. Rev. B 95, 174101] Published Tue May 09, 2017

]]>Crystal truncation rods are used to study surface and interface structure. Since real surfaces are always somewhat miscut from a low index plane, it is important to study the effect of miscuts on crystal truncation rods. We develop a model that describes the truncation rod scattering from miscut sur...

[Phys. Rev. B 95, 184104] Published Mon May 08, 2017

]]>Controlling material properties by modulating the crystalline structure has been attempted using various techniques, e.g., hydrostatic pressure, chemical pressure, and epitaxy. These techniques succeed to improve properties and achieve desired functionalities by changing the unit cell in all dimensi...

[Phys. Rev. B 95, 184105] Published Mon May 08, 2017

]]>We demonstrate that the instability of the Sb vacancy in GaSb leads to a further increase in the acceptor-type defect concentration in proton irradiated undoped, $p$-type GaSb. Using positron annihilation spectroscopy *in situ* with 10 MeV proton irradiation at 35 K, we find that the irradiation produce...

[Phys. Rev. B 95, 184103] Published Wed May 03, 2017

]]>Layered transition metal dichalcogenides ${\mathrm{MoTe}}_{2}$ and ${\mathrm{WTe}}_{2}$ share almost similar lattice constants as well as topological electronic properties except their structural phase transitions. While the former shows a first-order phase transition between monoclinic and orthorhombic structures, the latter does...

[Phys. Rev. B 95, 180101(R)] Published Mon May 01, 2017

]]>Density-functional theory forces, stresses, and energies comprise a database from which the optimal parameters of a spline-based empirical potential combining Stillinger-Weber and modified embedded-atom forms are determined. The accuracy of the potential is demonstrated by calculations of ideal shea...

[Phys. Rev. B 95, 184101] Published Mon May 01, 2017

]]>First-principles calculations predict the emergence of magnetoelectric coupling mediated by two-dimensional electron gas (2DEG) at the ferroelectric ${\mathrm{PbTiO}}_{3}/{\mathrm{SrTiO}}_{3}$ heterostructure. Free electrons endowed by naturally existing oxygen vacancies in ${\mathrm{SrTiO}}_{3}$ are driven to the heterostructure interface unde...

[Phys. Rev. B 95, 184102] Published Mon May 01, 2017

]]>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

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