We study experimentally the intermittent progress of the mechanically induced martensitic transformation in a Cu-Al-Be single crystal through a full-field measurement technique: the grid method. We utilize an in-house, specially designed gravity-based device, wherein a system controlled by water pum...

[Phys. Rev. B 91, 174111] Published Tue May 26, 2015

]]>By using first principles in combination with atomistic spin dynamics calculational methods, we determine the temperature-dependent free energies of the $L{2}_{1}$- and $L{1}_{0}-{\mathrm{Ni}}_{2}\left({\mathrm{Mn}}_{1-x}{\mathrm{Fe}}_{x}\right)\text{Ga}\phantom{\rule{0.28em}{0ex}}\left(0\le x\le 1\right)$, including phonon vibrational and magnetic energies. The $x$-dependent martensitic phase transformation (MPT) tem...

[Phys. Rev. B 91, 174112] Published Tue May 26, 2015

]]>Using density functional theory calculations, many researchers have predicted that various tungsten nitride compounds ${\text{N}}_{1-x}{\text{W}}_{x}\left(x\frac{1}{2}\right)$ will be “ultraincompressible” or “superhard,” i.e., as hard as or harder than diamond. Necessary conditions for such compounds are that they have large bulk and shea...

[Phys. Rev. B 91, 184110] Published Tue May 26, 2015

]]>We propose a gravitational response theory for point defects (hedgehogs) binding Majorana zero modes in (3 + 1)-dimensional superconductors. Starting in 4 + 1 dimensions, where the point defect is extended into a line, a coupling of the bulk defect texture with the gravitational field is introduced....

[Phys. Rev. B 91, 184111] Published Tue May 26, 2015

]]>Thermodynamic Ginzburg-Landau potential for temperature- and stress-induced phase transformations (PTs) between $n$ phases is developed. It describes each of the PTs with a single order parameter without an explicit constraint equation, which allows one to use an analytical solution to calibrate each ...

[Phys. Rev. B 91, 174109] Published Thu May 21, 2015

]]>We studied solid solution effects on the mechanical properties of nanocrystalline (NC) ${\mathrm{Pd}}_{100-\mathrm{x}}{\mathrm{Au}}_{\mathrm{x}}$ alloys $(0\le x<50\phantom{\rule{0.16em}{0ex}}\phantom{\rule{0.16em}{0ex}}\mathrm{at}.\%)$ at the low end of the nanoscale. Concentration has been used as control parameter to tune material properties (elastic moduli, Burgers vector, stacking fault energies) at basicall...

[Phys. Rev. B 91, 174110] Published Thu May 21, 2015

]]>We present a scaling theory for the entanglement spectrum under an external driving. Based on the static scaling of the Schmidt gap and the theory of finite-time scaling, we show that the Schmidt gap can signal the critical point and be used to estimate the critical exponents no matter in the finite...

[Phys. Rev. B 91, 184109] Published Thu May 21, 2015

]]>Vacancy properties in concentrated alloys continue to be of great interest because nowadays *ab initio* supercell simulations reach a scale where even defect properties in disordered alloys appear to be within reach. We show that vacancy properties cannot generally be extracted from supercell total en...

[Phys. Rev. B 91, 174107] Published Wed May 20, 2015

]]>We present a comprehensive study of polar and magnetic excitations in ${\mathrm{BiFeO}}_{3}$ ceramics and a thin film epitaxially grown on an orthorhombic (110) ${\mathrm{TbScO}}_{3}$ substrate. Infrared reflectivity spectroscopy was performed at temperatures from 5 to 900 K for the ceramics and below room temperature for the thin...

[Phys. Rev. B 91, 174108] Published Wed May 20, 2015

]]>The structure and stability of defect clusters in ${\mathrm{LiNbO}}_{3}$, as well as their influence on the linear and nonlinear optical susceptibilities, are calculated within density functional theory (DFT) using semilocal and hybrid exchange-correlation functionals. In particular, the complexes modeling the Li s...

[Phys. Rev. B 91, 174106] Published Tue May 19, 2015

]]>We present a detailed study of an electric-field-induced phase transition of a single layer of Fe on a Ni(111) substrate. Scanning tunneling microscopy at 4 K substrate temperature is used to provide the necessary electric field and to follow the transition from face-centered cubic to hexagonal clos...

[Phys. Rev. B 91, 184107] Published Tue May 19, 2015

]]>Canonical and microcanonical Monte Carlo simulations are carried out to study the electrocaloric effect (ECE) in ferroelectrics and relaxor ferroelectrics (RFEs) by direct computation of field-induced temperature variations at the ferroelectric-to-paraelectric phase transition and the nonergodic-to-...

[Phys. Rev. B 91, 184108] Published Tue May 19, 2015

]]>The $\alpha \text{-Fe}\leftrightarrow \epsilon \text{-Fe}$ pressure-induced transformation under pure hydrostatic static compression has been characterized with *in situ* x-ray diffraction using $\alpha \text{-Fe}$ single crystals as starting samples. The forward transition starts at 14.9 GPa, and the reverse at 12 GPa, with a width of $\alpha -\epsilon $ coexistence domain o...

[Phys. Rev. B 91, 174105] Published Thu May 14, 2015

]]>The coexistence pressure of two phases is a well-defined point at fixed temperature. In experiment, however, due to nonhydrostatic stresses and a stress-dependent potential energy barrier, different measurements yield different ranges of pressure with a hysteresis. Accounting for these effects, we p...

[Phys. Rev. B 91, 174104] Published Tue May 12, 2015

]]>We demonstrate experimentally the possibility of revealing fluctuations in the eigenfrequency of a resonator when the frequency noise is of the telegraph type. Using a resonantly driven micromechanical resonator, we show that the time-averaged vibration amplitude spectrum exhibits two peaks. They me...

[Phys. Rev. B 91, 174102] Published Mon May 11, 2015

]]>There are ample experimental evidences indicating that the ferroelastic domain walls of incipient ferroelectrics, such as $\mathrm{SrTi}{\mathrm{O}}_{3}$ and $\mathrm{CaTi}{\mathrm{O}}_{3}$, are polar. The emergence of such interfacial polar order at a domain wall is exciting and believed to arise from the coupling between a primary order parameter...

[Phys. Rev. B 91, 174103] Published Mon May 11, 2015

]]>Despite their structural similarities, ${\mathrm{SrBi}}_{2}{\mathrm{Ta}}_{2}{\mathrm{O}}_{9}$ (SBT) and ${\mathrm{SrBi}}_{2}{\mathrm{Nb}}_{2}{\mathrm{O}}_{9}$ (SBN) undergo a different sequence of phase transitions. The phase diagram of SBT as a function of the temperature includes an intermediate phase between the high-temperature phase and the ferroelectric ground state, while in the...

[Phys. Rev. B 91, 184106] Published Mon May 11, 2015

]]>We investigated the crystal and electronic structures of ferroelectric $\mathrm{B}{\mathrm{i}}_{4}\mathrm{T}{\mathrm{i}}_{3}{\mathrm{O}}_{12}$ single-crystalline thin films site-specifically substituted with $\mathrm{LaCo}{\mathrm{O}}_{3}$ (LCO). The epitaxial films were grown by pulsed laser epitaxy on $\mathrm{NdGa}{\mathrm{O}}_{3}$ and $\mathrm{SrTi}{\mathrm{O}}_{3}$ substrates to vary the degree of strain. With increasing the LCO...

[Phys. Rev. B 91, 174101] Published Fri May 08, 2015

]]>Domain pattern variations with temperature were studied by polarizing light microscopy for the morphotropic phase boundary composition $0.67\mathrm{Pb}(\mathrm{M}{\mathrm{g}}_{1/3}\mathrm{N}{\mathrm{b}}_{2/3}){\mathrm{O}}_{3}-0.33\mathrm{PbTi}{\mathrm{O}}_{3}$ (PMN-0.33PT) single crystal. At room temperature, the monoclinic ${\mathrm{M}}_{\mathrm{A}}$ phase is the dominant phase in the unpoled crystal, which coexist...

[Phys. Rev. B 91, 184105] Published Fri May 08, 2015

]]>Solid-state amorphization of crystalline copper nanolayers embedded in a ${\mathrm{Cu}}_{64}{\mathrm{Zr}}_{36}$ metallic glass is studied by molecular dynamics simulations for different orientations of the crystalline layer. We show that solid-state amorphization is driven by a reduction of interface energy, which compensates th...

[Phys. Rev. B 91, 184103] Published Wed May 06, 2015

]]>We derive a method to determine the effective local elasticity tensor by combining the local stress, local strain, and global strain in conjunction with a linear least-squares solver. This method reduces to the standard stress-strain fluctuation method for the estimation of global moduli if the loca...

[Phys. Rev. B 91, 184104] Published Wed May 06, 2015

]]>The intergrowth crystal of $n$-tetracosane/urea presents a misfit parameter, defined by the ratio $\gamma ={c}_{h}/{c}_{g}({c}_{\mathrm{host}}/{c}_{\mathrm{guest}})$, that is very close to a commensurate value $(\gamma \cong 1/3)$. High-resolution diffraction studies presented here reveal an aperiodic misfit parameter of $\gamma =0.3369$, which is found to be constan...

[Phys. Rev. B 91, 184101] Published Tue May 05, 2015

]]>The stress fields of dislocations predicted by classical elasticity are known to be unrealistically large approaching the dislocation core, due to the singular nature of the theory. While in many cases this is remedied with the approximation of an effective core radius, inside which ad hoc regulariz...

[Phys. Rev. B 91, 184102] Published Tue May 05, 2015

]]>Understanding the ionic conduction in solid electrolytes in contact with electrodes is vitally important to many applications, such as lithium ion batteries. The problem is complex because both the internal properties of the materials (e.g., electronic structure) and the characteristics of the exter...

[Phys. Rev. B 91, 134116] Published Thu Apr 30, 2015

]]>Single crystal neutron diffraction is combined with synchrotron x-ray scattering to identify the different superlattice phases present in ${\text{Cs}}_{0.8}{\text{Fe}}_{1.6}{\text{Se}}_{2}$. A combination of single crystal refinements and first principles modeling are used to provide structural solutions for the $\sqrt{5}\times \sqrt{5}$ and $\sqrt{2}\times \sqrt{2}$ superlattice...

[Phys. Rev. B 91, 144114] Published Thu Apr 30, 2015

]]>Investigation of the wavelength dependence (725–1025 nm) of the threshold for nanosecond optical breakdown in water revealed steps consistent with breakdown initiation by multiphoton ionization, with an initiation energy of about 6.6 eV. This value is considerably smaller than the autoionization thr...

[Phys. Rev. B 91, 134114] Published Wed Apr 29, 2015

]]>Antiferroelectrics are under extensive reexamination owing to their unique properties and technological promise. Computationally, they pose a challenge for predictive modeling as they often do not possess well-defined localized electric moments and exhibit a delicate energetic balance between polar ...

[Phys. Rev. B 91, 134112] Published Mon Apr 27, 2015

]]>The interaction of grain boundaries with ferroelectric domain walls strongly influences the extrinsic contribution to piezoelectric activity in $\mathrm{Pb}{\mathrm{Zr}}_{1-x},{\mathrm{Ti}}_{x}{\mathrm{O}}_{3}$ (PZT), ubiquitous in modern transducers and actuators. However, the fundamental understanding of these phenomena has been limited by complex m...

[Phys. Rev. B 91, 134113] Published Mon Apr 27, 2015

]]>We employ first-principles calculations to study the atomic and electronic structure of various point defects such as vacancies, interstitials, and antisites in the stoichiometric as well as slightly off-stoichiometric ${\mathrm{Ti}}_{1-c}{\mathrm{C}}_{c}$ (including both C-poor and C-rich compositions, $0.49\le c\le 0.51$). The atomic ...

[Phys. Rev. B 91, 134111] Published Fri Apr 24, 2015

]]>The high pressure structural and electronic evolution of bulk ${\mathrm{MoS}}_{2}$, an important transition metal layered dichalchogenide, is currently under active investigation, particularly in search of superconductivity. Recent theoretical and experimental work predicted and verified a $2{H}_{c}\to 2{H}_{a}$ layer sliding str...

[Phys. Rev. B 91, 144113] Published Thu Apr 23, 2015

]]>Mixtures of light elements with heavy elements are important in inertial confinement fusion. We explore the physics of molecular scale mixing through a validation study of equation of state (EOS) properties. Density functional theory molecular dynamics (DFT-MD) at elevated temperature and pressure i...

[Phys. Rev. B 91, 134109] Published Wed Apr 22, 2015

]]>Electron paramagnetic resonance (EPR) is used to identify a new and unique photoactive silicon-related point defect in single crystals of rutile $\mathrm{Ti}{\mathrm{O}}_{2}$. The importance of this defect lies in its assignment to interstitial silicon ions and the unexpected establishment of silicon impurities as a major h...

[Phys. Rev. B 91, 134110] Published Wed Apr 22, 2015

]]>Between 19 and 54 GPa, potassium has a complex composite incommensurate host-guest structure which undergoes two intraphase transitions over this pressure range. The temperature dependence of these host-guest phases is further complicated by the onset of an order-disorder transition in their guest c...

[Phys. Rev. B 91, 144111] Published Wed Apr 22, 2015

]]>The local atomic structure of the new nonmagnetic superconducting system ${\text{LaO}}_{1-x}{\text{F}}_{x}{\text{BiS}}_{2}$ is investigated using neutron diffraction and the pair density function analysis. Evidence for local charge fluctuations linked to a charge disproportionation of the Bi ions in the distorted lattice of superconduct...

[Phys. Rev. B 91, 144112] Published Wed Apr 22, 2015

]]>The high pressure-temperature behavior of titanium has been studied with x-ray diffraction in resistively heated and laser-heated diamond anvil cells up to 200 GPa and $\sim 3500$ K. The stability fields of $\alpha \text{\u2212}\mathrm{Ti},\omega \text{\u2212}\mathrm{Ti},\beta \text{\u2212}\mathrm{Ti},\gamma \text{\u2212}\mathrm{Ti}$, and $\delta \text{\u2212}\mathrm{Ti}$ have been determined in this range. $\gamma \text{\u2212}\mathrm{Ti}$ and $\delta \text{\u2212}\mathrm{Ti}$, which had been evi...

[Phys. Rev. B 91, 134108] Published Tue Apr 21, 2015

]]>The field-induced polarization reversal in the $c$-oriented ferroelectric phase of strained perovskite film has been studied. We show that in addition to the conventional longitudinal switching mechanism, when the $c$-oriented polarization vector changes its modulus, the longitudinal-transversal and tra...

[Phys. Rev. B 91, 144110] Published Tue Apr 21, 2015

]]>We report on theoretical and experimental investigation of $A$-site-driven ferroelectricity in ferromagnetic ${\mathrm{La}}_{2}{\mathrm{NiMnO}}_{6}$ thin films grown on ${\mathrm{SrTiO}}_{3}$ substrates. Structural analysis and density-functional theory calculations show that epitaxial strain stretches the rhombohedral ${\mathrm{La}}_{2}{\mathrm{NiMnO}}_{6}$ crystal lattice a...

[Phys. Rev. B 91, 134107] Published Mon Apr 20, 2015

]]>Inelastic scattering of electrons on crystals can excite lattice vibrations known as phonons. An energy resolution of 10 meV in the scattered electron energy loss has recently been demonstrated in scanning transmission electron microscopy (STEM), permitting experimenters to distinguish between elastic and inelastic scattering events. In this paper the authors present simulations showing that, with the recent improvement in energy resolution, atomic resolution phonon spectroscopy and imaging of crystals using STEM should now be feasible.

[Phys. Rev. B 91, 144108] Published Mon Apr 20, 2015

]]>We study the dynamics of inorganic antiferroelectric nanoclusters formed during an order-disorder transition and demonstrate the coexistence of the two phases in a region of 2–3 K around the transition temperature ${T}_{N}\sim 215$ K. Single crystals of ${\mathrm{NH}}_{4}{\mathrm{H}}_{2}{\mathrm{AsO}}_{4}$, a model hydrogen-bonded compound, show an anti...

[Phys. Rev. B 91, 140102(R)] Published Fri Apr 17, 2015

]]>The orientation-dependent equilibrium ferroelectric domain structures and dielectric properties of polydomain ${\mathrm{PbZr}}_{1}{}_{-}{}_{x}{\mathrm{Ti}}_{x}{\mathrm{O}}_{3}$ thin films are investigated using a phenomenological Ginzburg-Landau-Devonshire thermodynamic model. We develop and describe three-dimensional polydomain models for (001)-, (101...

[Phys. Rev. B 91, 144106] Published Fri Apr 17, 2015

]]>We employ the quasiharmonic approximation to study the temperature-dependent lattice dynamics of the four different phases of cesium tin iodide $\left({\mathrm{CsSnI}}_{3}\right)$. Within this framework, we obtain the temperature dependence of a number of structural properties, including the cell volume, bulk modulus, and Grü...

[Phys. Rev. B 91, 144107] Published Fri Apr 17, 2015

]]>We demonstrate an innovative multifunctional artificial material that combines exotic metamaterial properties and the environmentally responsive nature of phase-change media. The tunable metamaterial is designed with the aid of two interwoven coordinate-transformation equations and implemented with ...

[Phys. Rev. B 91, 134105] Published Thu Apr 16, 2015

]]>The origin of the relaxor behavior in ${\mathrm{K}}_{1-x}{\mathrm{Li}}_{x}{\mathrm{TaO}}_{3}\phantom{\rule{0.28em}{0ex}}\left(\mathrm{KLT}\right)$ and other disordered perovskites is now recognized to be due to the reorientation of the polar nanodomains formed by the correlated dipoles of off-center ions. The collective dynamics of these systems evolve through several temperature stages. O...

[Phys. Rev. B 91, 134106] Published Thu Apr 16, 2015

]]>We study a minimal model for a relaxor ferroelectric including dipolar interactions and short-range harmonic and anharmonic forces for the critical modes as in the theory of pure ferroelectrics together with quenched disorder coupled linearly to the critical modes. We present the simplest approximat...

[Phys. Rev. B 91, 144105] Published Tue Apr 14, 2015

]]>Using first-principles computational techniques, we have investigated the structural, vibrational, and dielectric properties of a Ruddlesden-Popper-type layered oxide ${\mathrm{Ba}}_{2}{\mathrm{ZrO}}_{4}$ subjected to a wide range of biaxial strains emulating epitaxial thin-film environment. Under compressive strains, this compo...

[Phys. Rev. B 91, 134103] Published Mon Apr 13, 2015

]]>The effect of octahedral tilting on the acentric structural transitions in $A\mathrm{Ga}{\mathrm{O}}_{3}/{A}^{\prime}\mathrm{Ga}{\mathrm{O}}_{3}$ [001], [110], and [111] superlattices $(A,{A}^{\prime}=\mathrm{La},\mathrm{Pr},\mathrm{Nd})$ is studied using density functional theory. We find the displacive transitions are driven by two octahedral rotations modes (${a}^{-}{a}^{-}{c}^{0}$ and ${a}^{0}{a}^{0}{c}^{+}$ tilting) with a...

[Phys. Rev. B 91, 134104] Published Mon Apr 13, 2015

]]>The interacting bosons in one-dimensional inversion-symmetric superlattices are investigated from the topological aspect. The complete phase diagram is obtained by an atomic-limit analysis and quantum Monte Carlo simulations and comprises three kinds of phases: superfluid, persisted charge-density-w...

[Phys. Rev. B 91, 134101] Published Fri Apr 10, 2015

]]>Metamaterial effective parameters may exhibit freedom from typical dispersion constraints. For instance, the emergence of a magnetic response in arrays of split ring resonators for long wavelengths cannot be attained in a passive continuous system obeying the Kramers-Kronig relations. We characteriz...

[Phys. Rev. B 91, 134102] Published Fri Apr 10, 2015

]]>Electric fields are generally known to favor the ferroelectric polar state over the antiferroelectric nonpolar state for their Coulomb interactions with dipoles in the crystal. In this paper, we directly image an electric-field-assisted ferroelectric-to-antiferroelectric phase transition during pola...

[Phys. Rev. B 91, 144104] Published Fri Apr 10, 2015

]]>Density functional theory calculations of the vibrational modes of ${\mathrm{Bi}}_{12}{\mathrm{SiO}}_{20}$ are presented, with a detailed assignment and geometry investigation of the vibrational modes in the sillenite structure. We show that the symmetry and geometry of the strong Raman peaks allow direct probing of the Bi-O(1) ...

[Phys. Rev. B 91, 144103] Published Thu Apr 09, 2015

]]>We propose an approach to the problem of lattice distortions at low temperatures and ambient pressure in the solid hydrogens in their rotational ground states that explicitly accounts for the molecular nature of the constituent particles. The model is based on the idea that the second-order rotation...

[Phys. Rev. B 91, 144102] Published Wed Apr 08, 2015

]]>Series of high-pressure x-ray diffraction patterns of iron and its high-pressure polymorphs were collected with 0.1–0.2-s exposure time utilizing a membrane diamond anvil cell (DAC) for compression at various loading and unloading rates to a maximum pressure of 70 GPa. Strain rates of ${10}^{-2}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{-1}$ at a m...

[Phys. Rev. B 91, 144101] Published Tue Apr 07, 2015

]]>Synchrotron-radiation-based Mössbauer absorption spectroscopy of ${}^{40}\mathrm{K}$ nuclei was performed. We investigated potassium nanoclusters arrayed in a porous crystal of sodalite. The nanoclusters exhibit antiferromagnetic (AFM) ordering below $\simeq 72$ K. The energy-domain ${}^{40}\mathrm{K}$ Mössbauer spectra were successfully ...

[Phys. Rev. B 91, 140101(R)] Published Mon Apr 06, 2015

]]>We report the results of pressure-induced phase transitions and metallization in ${\mathrm{VO}}_{2}$ based on synchrotron x-ray diffraction, electrical resistivity, and Raman spectroscopy. Our isothermal compression experiments at room temperature and 383 K show that the room temperature monoclinic phase $(M1,\phantom{\rule{0.16em}{0ex}}P{2}_{1}/c)$...

[Phys. Rev. B 91, 104110] Published Tue Mar 31, 2015

]]>The pressure-induced phase transition of the multiferroic manganese tungstate ${\mathrm{MnWO}}_{4}$ is studied on single crystals using synchrotron x-ray diffraction and Raman spectroscopy. We observe the monoclinic $P2/c$ to triclinic $P\overline{1}$ phase transition at 20.1 GPa and get insight on the phase transition mechanism...

[Phys. Rev. B 91, 104109] Published Mon Mar 30, 2015

]]>Relaxor-based ferroelectrics have been known for decades to possess a relatively thick surface layer (“skin”) that is distinct from its interior. Yet while there is consensus about its existence, there are controversies about its symmetry, phase stability, and origin. In an attempt to clarify these ...

[Phys. Rev. B 91, 094111] Published Thu Mar 26, 2015

]]>Chiral crystals come in left- and right-handed forms. Methods for using electron diffraction to determine crystal chirality have heretofore required the use of multiple scattering and depended sensitively on the sample thickness. Here it is shown that these constraints can be removed with the use of electron vortex beams (which carry orbital angular momentum) in a transmission electron microscope. In accordance with theoretical expectation, the chirality of a sample of Mn${}_{2}$Sb${}_{2}$O${}_{7}$ is experimentally determined.

[Phys. Rev. B 91, 094112] Published Thu Mar 26, 2015

]]>${\mathrm{Th}}_{3}{\mathrm{Ir}}_{4}{\mathrm{Ge}}_{13}$ and ${\mathrm{U}}_{3}{\mathrm{Ir}}_{4}{\mathrm{Ge}}_{13}$ crystallize with primitive cubic ${\mathrm{Tm}}_{3}{\mathrm{Co}}_{4}{\mathrm{Ge}}_{13}$ and noncentrosymmetric rhombohedral ${\text{HT-Y}}_{3}{\mathrm{Pt}}_{4}{\mathrm{Ge}}_{13}$ type of structures, respectively, which are derivatives of the cubic ${\mathrm{Yb}}_{3}{\mathrm{Rh}}_{4}{\mathrm{Sn}}_{13}$ prototype. Measurements of magnetic susceptibility, electrical resistivity, specific heat, thermopower...

[Phys. Rev. B 91, 094110] Published Wed Mar 18, 2015

]]>Iron doped ${\text{LiNbO}}_{3}$ crystals with different iron valence states are investigated. An extended x-ray absorption fine structure (EXAFS) spectroscopy study highlights evident changes in the local structure around iron that can be ascribed to the presence of small polarons. In particular, when a ${\text{Fe}}^{3+}$ repl...

[Phys. Rev. B 91, 094109] Published Tue Mar 17, 2015

]]>A roadblock in utilizing III-V semiconductors for scaled-down electronic devices is their poor dopant activation. As a first step to unravel the dopant behavior in InGaAs, we studied the tendency for dopant formation computationally using two approaches: *ab initio* and semiempirical methods. We studi...

[Phys. Rev. B 91, 094108] Published Mon Mar 16, 2015

]]>The diffusionless pseudobinary phase diagram, monodomain properties, and free energy of $(1-x)\mathrm{Ba}(\mathrm{Z}{\mathrm{r}}_{0.2}\mathrm{T}{\mathrm{i}}_{0.8}){\mathrm{O}}_{3}\text{\u2212}x\left(\mathrm{B}{\mathrm{a}}_{0.7}\mathrm{C}{\mathrm{a}}_{0.3}\right)\mathrm{Ti}{\mathrm{O}}_{3}$ are computed for comparison with experimental results. Specifically, the variation of the spontaneous polarization, anisotropy energy, and free energy with respect to tempe...

[Phys. Rev. B 91, 104108] Published Mon Mar 16, 2015

]]>We have performed *ab initio* band-structure calculations on more than 2000 half-Heusler compounds in order to search for new candidates for topological insulators. Herein, LiAuS and NaAuS are found to be the strongest topological insulators with the bulk band gaps of 0.20 and 0.19 eV, respectively, d...

[Phys. Rev. B 91, 094107] Published Thu Mar 12, 2015

]]>Using all-atom molecular dynamics (MD) simulations, we have studied the mechanical properties of ZnS/CdS core/shell nanowires. Our results show that the coating of a few-atomic-layer CdS shell on the ZnS nanowire leads to a significant change in the stiffness of the core/shell nanowires compared to ...

[Phys. Rev. B 91, 104107] Published Thu Mar 12, 2015

]]>The atomistic study of kink pairs on screw dislocations in body-centered cubic (bcc) metals is challenging because interatomic potentials in bcc metals still lack accuracy and kink pairs require too many atoms to be modeled by first principles. Here, we circumvent this difficulty using a one-dimensi...

[Phys. Rev. B 91, 094105] Published Mon Mar 09, 2015

]]>We propose a method to evaluate the diffusion coefficient of vacancy-hydrogen clusters (${\mathrm{VH}}_{n})$ in metals. The key is a good separation of time scales between H diffusion and the metal-vacancy exchange. The Ni-H system is investigated in details, using *ab initio* calculations, but the arguments can be t...

[Phys. Rev. B 91, 094106] Published Mon Mar 09, 2015

]]>Molecular dynamics simulations using a first-principles-derived effective Hamiltonian are conducted on lead zirconium titanate ultrathin films possessing nanoscale ferroelectric domains and experiencing a GHz electric field. Pulses of magnetization are predicted to occur in this system when sudden c...

[Phys. Rev. B 91, 100101(R)] Published Mon Mar 09, 2015

]]>The dielectric and piezoelectric properties of an epitaxial $\mathrm{PbZ}{\mathrm{r}}_{0.8}\mathrm{T}{\mathrm{i}}_{0.2}{\mathrm{O}}_{3}/\mathrm{PbZ}{\mathrm{r}}_{0.6}\mathrm{T}{\mathrm{i}}_{0.4}{\mathrm{O}}_{3}$ ferroelectric bilayer film were studied. Time-resolved synchrotron x-ray microdiffraction provided access to layer-specific structural information during electric-field-induced changes. The observed dielectric ...

[Phys. Rev. B 91, 104106] Published Mon Mar 09, 2015

]]>For decades it has been a well-known fact that among the few ferroelectric compounds in the perovskite family, namely, ${\mathrm{BaTiO}}_{3}$, ${\mathrm{KNbO}}_{3}$, ${\mathrm{PbTiO}}_{3}$, and ${\mathrm{Na}}_{1/2}{\mathrm{Bi}}_{1/2}{\mathrm{TiO}}_{3}$, the dielectric and piezoelectric properties of ${\mathrm{BaTiO}}_{3}$ are considerably higher than the others in polycrystalline form at room temperature....

[Phys. Rev. B 91, 104104] Published Thu Mar 05, 2015

]]>We calculate the thermomechanical properties of $\alpha $-iron, and in particular its isothermal and adiabatic elastic constants, using first-principles total-energy and lattice-dynamics calculations, minimizing the quasiharmonic vibrational free energy under finite strain deformations. Particular care is m...

[Phys. Rev. B 91, 104105] Published Thu Mar 05, 2015

]]>We present a detailed mechanism of, and the effect of homogeneous strains on, the migration of uranium vacancies in ${\mathrm{UO}}_{2}$. Vacancy migration pathways and barriers are identified using density functional theory and the effect of uniform strain fields are accounted for using the dipole tensor approach. ...

[Phys. Rev. B 91, 094103] Published Tue Mar 03, 2015

]]>This paper summarizes 0 to 0.6 GPa neutron diffraction measurements of a nickel hexacyanochromate coordination polymer (NiCrPB) that has the face-centered-cubic, Prussian blue structure. Deuterated powders of NiCrPB contain $\approx 100$-nm-sided cubic particles. The application of a large magnetic field sho...

[Phys. Rev. B 91, 094104] Published Tue Mar 03, 2015

]]>In this paper we study the growth properties of domains of low-spin molecules in a high-spin background in open-boundary elliptically shaped spin-crossover systems within the framework of a mechanoelastic model. The molecules are situated on a triangular lattice and are linked by springs, through wh...

[Phys. Rev. B 91, 104102] Published Tue Mar 03, 2015

]]>Flexoelectricity is a universal property of all dielectrics by which they generate a voltage in response to an inhomogeneous deformation. One of the controversial issues in this field concerns the magnitude of flexoelectric coefficients measured experimentally, which greatly exceed theoretical estim...

[Phys. Rev. B 91, 104103] Published Tue Mar 03, 2015

]]>Simulations of defects in paramagnetic materials at high temperature constitute a formidable challenge to solid-state theory due to the interaction of magnetic disorder, vibrations, and structural relaxations. CrN is a material where these effects are particularly large due to a strong magnetolattic...

[Phys. Rev. B 91, 094101] Published Mon Mar 02, 2015

]]>The normal modes of a continuum solid endowed with a random distribution of line defects that behave like elastic strings are described. These strings interact with elastic waves in the bulk, generating wave dispersion and attenuation. Explicit formulas are provided that relate these properties to t...

[Phys. Rev. B 91, 094102] Published Mon Mar 02, 2015

]]>*Ab initio* random structure searching (AIRSS) and density functional theory methods are used to predict structures of calcium and magnesium carbonate $({\mathrm{CaCO}}_{3}$ and ${\mathrm{MgCO}}_{3})$ at high pressures. We find a previously unknown ${\mathrm{CaCO}}_{3}$ structure which is more stable than the aragonite and “post aragonite” phases i...

[Phys. Rev. B 91, 104101] Published Mon Mar 02, 2015

]]>Using real-space density functional theory, electronic structure and equilibrium geometries of sodium clusters in the size range of 2–20 atoms have been calculated as a function of confinement. We have examined the evolution of the five lowest isomers as a function of volume for six different compre...

[Phys. Rev. B 91, 054112] Published Thu Feb 26, 2015

]]>As is known from visible-light experiments, silicon under femtosecond pulse irradiation can undergo so-called “nonthermal melting” if the density of electrons excited from the valence to the conduction band overcomes a certain critical value. Such ultrafast transition is induced by strong changes in...

[Phys. Rev. B 91, 054113] Published Thu Feb 26, 2015

]]>The recent surge of interest in phase-change materials GeTe, ${\mathrm{Ge}}_{2}{\mathrm{Sb}}_{2}{\mathrm{Te}}_{5}$, and related compounds motivated us to revisit the structural phase transition in GeTe in more detail than was done before. The rhombohedral-to-cubic ferroelectric phase transition in GeTe has been studied using high-resolution n...

[Phys. Rev. B 91, 054110] Published Wed Feb 25, 2015

]]>In this paper we investigate the acoustic-to-optical up-conversion phonon processes in a multicomponent system. These processes take place during heat transport and limit the efficiency of heat flow. By combining time-resolved optical and heat capacity experiments we quantify the thermal coupling co...

[Phys. Rev. B 91, 054111] Published Wed Feb 25, 2015

]]>The atomic structure of metallic glasses (MGs) plays an important role in their properties. Numerous molecular dynamics (MD) simulations have revealed icosahedral short-range order (ISRO) as a dominant motif in Cu-Zr metallic glasses. However, the cooling rates utilized in most of the MD simulations...

[Phys. Rev. B 91, 064105] Published Mon Feb 23, 2015

]]>As the first experimentally confirmed ferroelectric metal, ${\mathrm{LiOsO}}_{3}$ has received extensive research attention recently. Using density-functional calculations, we perform a systematic study on the origin of the metallic ferroelectricity in ${\mathrm{LiOsO}}_{3}$. We confirm that the ferroelectric transition in this co...

[Phys. Rev. B 91, 064104] Published Fri Feb 20, 2015

]]>Silicon nitride is a bulk and a coating material exhibiting excellent mechanical properties. We present a transferable reduced tight-binding (TB) model for the silicon nitride system, developed within the framework of coarse graining the electronic structure from density-functional theory (DFT) to t...

[Phys. Rev. B 91, 054109] Published Thu Feb 19, 2015

]]>Using the Landau theory we demonstrate the possibility of unusual, anomalously thick ferroelectric domain walls, where the order parameter rotates with a nearly constant modulus as in ferromagnets. The effect occurs in ${90}^{\circ}$ charged domain walls and is associated with the easy polarization rotation ne...

[Phys. Rev. B 91, 060102(R)] Published Wed Feb 18, 2015

]]>${\text{BaSi}}_{2}$-type disilicides and digermanides hold great promise for solar-cell applications, but their structural stability and phase transition mechanisms remain unresolved. Here we present *ab initio* calculations of pressure-induced structural phase transitions of ${\mathrm{BaSi}}_{2},{\mathrm{BaGe}}_{2}$, and ${\mathrm{SrGe}}_{2}$ and show that Si...

[Phys. Rev. B 91, 054107] Published Tue Feb 17, 2015

]]>On-the-fly kinetic Monte Carlo simulations are performed to investigate slow relaxation of nonequilibrium systems. Point defects induced by 25 keV cascades in $\alpha $-Fe are shown to lead to a characteristic time evolution, described by the replenish-and-relax mechanism. Then, we produce an atomistically ...

[Phys. Rev. B 91, 054108] Published Tue Feb 17, 2015

]]>The size dependence of plastic flow is studied by discrete dislocation dynamical simulations of systems with various amounts of interacting dislocations while the stress is slowly increased. The regions between avalanches in the individual stress curves as functions of the plastic strain were found ...

[Phys. Rev. B 91, 054106] Published Fri Feb 13, 2015

]]>We introduce the cluster-expansion ghost-lattice method, which extends the applicability of existing cluster-expansion software, to cluster expand structures of arbitrary finite and infinite geometries in a fast, unique, and transferable way. The ghost site that is introduced zeroes the cluster func...

[Phys. Rev. B 91, 054105] Published Thu Feb 12, 2015

]]>We investigated the atomistic structure of metallic glasses subjected to thermomechanical creep deformation using high energy x-ray diffraction and molecular dynamics simulation. The experiments were performed *in situ* at high temperatures as a time dependent deformation in the elastic regime, and *ex...*

[Phys. Rev. B 91, 060101(R)] Published Wed Feb 11, 2015

]]>We present a comprehensive density functional theory (DFT) -based study of different aspects of one vacancy and He impurity atom behavior at semicoherent interfaces between the low-solubility transition metals Cu and Nb. Such interfaces have not been previously modeled using DFT. A thorough analysis...

[Phys. Rev. B 91, 064103] Published Wed Feb 11, 2015

]]>The motion of domain walls (DWs) is critical to switching kinetics in ferroelectric (FE) materials. Merz's law, dependent only on the applied electric field, cannot explain recent experimental observations in FE thin films because these experiments showed that the DW velocity depends not only on the...

[Phys. Rev. B 91, 054104] Published Mon Feb 09, 2015

]]>Manganese-substitution-doped iron nitride ${\text{MnFe}}_{3}\text{N}$ holds great promise for applications in high-density magnetic recording and spintronic devices. However, existing theory contradicts experimental results on the structural and magnetic stability of ${\text{MnFe}}_{3}\text{N}$, and the underlying mechanisms remain elusive....

[Phys. Rev. B 91, 064102] Published Thu Feb 05, 2015

]]>We report on observation of ferroelastic domain structure in single crystals of multiferroic ${\text{CaMn}}_{7}{\text{O}}_{12}$ at room temperature. Two types of ferroelastic domain wall are found, consistent with the material's rhombohedral symmetry that is reduced from cubic symmetry at higher temperatures. Using Raman spe...

[Phys. Rev. B 91, 054102] Published Tue Feb 03, 2015

]]>Bosons interacting repulsively on a lattice with a flat lowest band energy dispersion may, at sufficiently small filling factors, enter into a Wigner-crystal-like phase. This phase is a consequence of the dispersionless nature of the system, which in turn implies the occurrence of single-particle lo...

[Phys. Rev. B 91, 054103] Published Tue Feb 03, 2015

]]>A synchrotron x-ray diffraction study of metal-insulator transitions in W-doped ${\text{VO}}_{2}\left({\text{V}}_{1-x}{\text{W}}_{x}{\text{O}}_{2}\right)$ thin films has been carried out. The insulating phase for $x\le 0.07$ exhibits cell-doubling with the V dimerization similar to bulk ${\text{VO}}_{2}$, while the insulating phase for $x\ge 0.11$ does not. This result suggests tha...

[Phys. Rev. B 91, 064101] Published Tue Feb 03, 2015

]]>Structural phase transitions in epitaxial stoichiometric $\mathrm{VN}/\mathrm{MgO}(011)$ thin films are investigated using temperature-dependent synchrotron x-ray diffraction (XRD), selected-area electron diffraction (SAED), resistivity measurements, high-resolution cross-sectional transmission electron microscopy, and...

[Phys. Rev. B 91, 054101] Published Mon Feb 02, 2015

]]>The linear dependence on temperature $\left(\gamma T\right)$ of the heat capacity at low temperatures $(T<15\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ is traditionally attributed to conduction electrons in metals; however, many insulators also exhibit a linear dependence that has been attributed to a variety of other physical properties. The property most...

[Phys. Rev. B 91, 024109] Published Thu Jan 29, 2015

]]>Lattice structures have long fascinated physicists and engineers not only because of their outstanding functionalities, but also for their ability to control the propagation of elastic waves. While the study of the relation between the connectivity of these systems and their static properties has a ...

[Phys. Rev. B 91, 020103(R)] Published Mon Jan 26, 2015

]]>A recently developed bounds-analysis approach has been used to interpret density-functional-theory (DFT) results for the As and Ga antisites in GaAs. The bounds analysis and subsequent processing of DFT results for the As antisite yielded levels—defined as the Fermi levels at which the defect charge...

[Phys. Rev. B 91, 014110] Published Fri Jan 23, 2015

]]>The phase stability of fcc and bcc magnetic binary Fe-Cr, Fe-Ni, and Cr-Ni alloys, and ternary Fe-Cr-Ni alloys is investigated using a combination of density functional theory (DFT), cluster expansion (CE), and magnetic cluster expansion (MCE) approaches. Energies, magnetic moments, and volumes of m...

[Phys. Rev. B 91, 024108] Published Fri Jan 23, 2015

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