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

]]>Carrier mobility in graphene can be degraded by roughness. Here, the authors have measured the roughness of a suspended graphene layer encapsulated with hexagonal boron nitride (hBN) by diffraction in the transmission electron microscope. The 12-pm roughness measured is close to that found for carbon atoms within graphite. The simulations here show that encapsulation localizes flexural phonons in the hBN layers, leading to a suppression of roughness in the graphene. These results could lead to new strategies for device fabrication in applications requiring ultimately high performance, and show that layer roughness in artificially fabricated van der Waals heterostructures approaches that in naturally occurring bulk crystals.

[Phys. Rev. B 96, 014101] Published Wed Jul 05, 2017

]]>We study the electrocaloric (EC) effect in bulk ${\mathrm{BaTiO}}_{3}$ (BTO) using molecular dynamics simulations of a first principles-based effective Hamiltonian, combined with direct measurements of the adiabatic EC temperature change in BTO single crystals. We examine in particular the dependence of the EC effe...

[Phys. Rev. B 96, 014102] Published Wed Jul 05, 2017

]]>The accuracy of $GW$ in the determination of defect energy levels is assessed through calculations on a set of well-characterized point defects in semiconductors: the As antisite in GaAs, the substitutional Mg in GaN, the interstitial C in Si, the Si dangling bond, and the Si split-vacancy complex in ...

[Phys. Rev. B 96, 020101(R)] Published Wed Jul 05, 2017

]]>The effects of W doping on the structure and optical properties of Aurivillius ferroelectric ${\mathrm{Na}}_{0.5}{\mathrm{Bi}}_{2.5}{\mathrm{Nb}}_{2}{\mathrm{O}}_{9}$-based ceramics have been investigated by x-ray diffraction, far-infrared reflectance, and spectroscopic ellipsometry (SE). Moreover, the temperature dependent lattice dynamics and electronic ...

[Phys. Rev. B 96, 024101] Published Wed Jul 05, 2017

]]>For decades, numerous attempts have been made to produce polar oxynitride perovskites, where some of the oxygen is replaced by nitrogen, but a polar ordered oxynitride has never been demonstrated. Caracas and Cohen [Appl. Phys. Lett. **91**, 092902 (2007)] studied possible ordered polar oxynitrides with...

[Phys. Rev. B 95, 214120] Published Fri Jun 30, 2017

]]>The effect of Ti and Hf impurities on the $\left(111\right)$ antiphase boundary (APB) energy of ${\mathrm{Ni}}_{3}\mathrm{Al}$ is investigated via *ab initio* calculations. Cluster expansion is performed to predict supercell total energies sampled in a Monte Carlo approach that accounts for nondilute point defects at finite temperature, o...

[Phys. Rev. B 95, 214121] Published Fri Jun 30, 2017

]]>Understanding the structural origins of the properties of amorphous materials remains one of the most important challenges in structural science. In this study, we demonstrate that local “structural simplicity”, embodied by the degree to which atomic environments within a material are similar to eac...

[Phys. Rev. B 95, 224108] Published Fri Jun 30, 2017

]]>We significantly improve the physical models underlying atomistic Monte Carlo (MC) simulations, through the use of *ab initio* fitted high-dimensional neural network potentials (NNPs). In this way, we can incorporate energetics derived from density functional theory (DFT) in MC, and avoid using empiri...

[Phys. Rev. B 95, 214117] Published Thu Jun 29, 2017

]]>The presence of a molecule at the $A$ site of an organic perovskite leads to unusual behavior compared to its inorganic counterpart. Considering the case of ${\mathrm{CH}}_{3}{\mathrm{NH}}_{3}$, we find that it is both the size of the molecule as well as its orientation in the cage formed by the Pb and Br atoms which determine the...

[Phys. Rev. B 95, 214118] Published Thu Jun 29, 2017

]]>I critically examine Goodenough's explanation for the experimentally observed phase transition in ${\mathrm{LiVO}}_{2}$ using microscopic calculations based on density functional and dynamical mean field theories. The high-temperature rhombohedral phase exhibits both magnetic and dynamical instabilities. Allowing a...

[Phys. Rev. B 95, 214119] Published Thu Jun 29, 2017

]]>In this paper, we use an elastic model in order to study the elastically driven cooperative switching of spin-crossover materials after femtosecond laser excitation. In this model, the molecules occupy a triangular lattice in open-boundary systems, and they are connected by springs. The volume chang...

[Phys. Rev. B 95, 224107] Published Thu Jun 29, 2017

]]>We evaluate the energetic stabilities of white, red, and black allotropes of phosphorus using density functional theory (DFT) and hybrid functional methods, van der Waals (vdW) corrections (DFT+vdW and hybrid+vdW), vdW density functionals, and random phase approximation (RPA). We find that stability...

[Phys. Rev. B 95, 214115] Published Wed Jun 28, 2017

]]>The equation of state $P(V,T)$ for solid argon is determined by the calculation of accurate static and vibrational terms in the free energy. The static component comes from a quantum theoretical many-body expansion summing over all energetic contributions from two-, three-, and four-body fragments tre...

[Phys. Rev. B 95, 214116] Published Wed Jun 28, 2017

]]>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

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