It is shown that self-consistent calculations of the electronic charge density in large periodic cells containing a single displaced atom provide all information needed for ab initio determination force constants, phonon dispersion curves, effective charges, and static dielectric constant. Results are presented GaAs.

We have performed density functional theory (DFT) calculations of iron−porphyrin (FeP) and its complexes with O2, CO, NO, imidazole (Im). Our fully optimized structures agree well the available experimental data for synthetic heme models. Comparison crystallographic proteins highlights interesting features carbon monoxymyoglobin. The diatomic molecule induces a 0.3−0.4 Å displacement Fe atom out porphyrin nitrogen (Np) plane doming overall ring. energy iron−diatomic bond increases in order...

Abstract The formalism of the deformable‐bond approximation, described in preceding article this series, is now applied to 15 compounds with zincblende structure. phonon dispersion curves and densities spectra are calculated for ZnS, ZnSe, GaP, GaAs, InSb, SiC, GuCl, CuI, method developed determination parameters characterizing model discussed. Analogous results obtained an 11‐parameter version rigid ion presented comparison.

We present results of "direct" calculations structure and lattice dynamics GaAs using local forms the ionic pseudopotentials density functional. The predicted constant, bulk modulus, phonon frequencies, effective charges, Gr\"uneisen parameters agree well with experiment. Eigenvectors at $X$ point are determined used to test phenomenological models. examine anharmonic energies suggest a possible transition under pressure an orthorhombic phase, related soft $\mathrm{TA}(X)$ phonon.

We present self-consistent calculations of the total energy, charge density, and electronic states "compensated" (100) interfaces Ge GaAs. In this paper we test methods using simplest compensated interfaces---an abrupt single mixed layer, either (1/2)(Ge + Ga) or As), "average atom" approximation for interface plane. The As) is found to be more stable (however, may an artifact averaging). find a large variation in dipole with stoichiometry. This not observed experimentally, suggesting that...

A new method is proposed for dealing with the dielectric response of a semiconductor to constant macroscopic electric field. The ``direct'' approach we use general, an alternative linear-response theory, and not restricted linear effects. It consists in incorporating field into system ``perturbed'' crystal as system; potential generated by building (periodically repeated) capacitor. We apply this Ge GaAs within local-density-functional framework investigate response: Macroscopic quantities...

A comprehensive phenomenological calculation is reported to understand the temperature- and pressure-dependent phonon properties in ZnS, ZnSe, ZnTe. Using pressure dependence of optical data established recently by Weinstein, we have constructed an 11-parameter rigid-ion model, which $p\ensuremath{\rightarrow}0$ limit goes over fitting neutron scattering results dispersions. Model calculations for lattice dynamics, frequency spectrum, mode gammas, Gr\"uneisen constant, linear...

It is shown that the macroscopic and microscopic dielectric responses to a constant electric field can be directly dealt with by method which general, alternative linear-response theory, not restricted linear effects. The basic features of theory are discussed; explicit calculations constant, miccroscopic local fields, transverse effective charges presented for Ge GaAs within local-density functional theory.

The recently found high-pressure phase of GaN is studied theoretically, using the density-functional theory. E(V) diagram set up from calculated total energies shows that crystal structure this rocksalt or NiAs, and energy bands indicate both modifications are semiconducting.

The effect of pressure on the zone-center optical phonon modes antimony in A7 structure has been investigated by Raman spectroscopy. A_g and E_g frequencies exhibit a pronounced softening with increasing pressure, being related to gradual suppression Peierls-like distortion phase relative cubic primitive lattice. Also, both broaden significantly under pressure. Spectra taken at low temperature indicate that broadening is least partly caused phonon-phonon interactions. We also report results...

La dynamique de réseau 15 composés présentant la structure blende est étudiée dans les termes du modèle Karo-Hardy. Celui-ci simplifié par une supposition concernant polarisabilités mécaniques, définissant ainsi l'Approximation des Liaisons Déformables, caractérisée 5 paramètres à long rayon d'action et 10 court d'action. Dans un but comparaison, modèles ions rigides 11 sont appliqués simultanément. Les courbes dispersion densités spectre phonons calculées, l'aide deux modèles, pour 8 : ceux...

The deformation-dipole-model (DDM) formalism is derived for a crystal of arbitrary symmetry and applied to the zinc-blende structure. In its present form, model more general than one proposed by Karo Hardy, principal difference consisting in introducing interactions called nonlocal electric polarizabilities, analogous shell-shell shell model. Both approaches are compared it shown that ionic crystals version DDM provides same description core motion as Parameters then expressed terms other...

The frequency-wave-vector dispersion relation $\ensuremath{\nu}(\stackrel{\ensuremath{\rightarrow}}{\mathrm{q}})$ for the normal vibrations of a CuCl single crystal at room temperature has been measured [100]-, [110]-, and [111]-symmetric directions using inelastic neutron scattering.

From high-resolution neutron-diffraction experiments we present equation-of-state (EOS) data of elemental lead as functions both temperature (80--298 K) and applied pressure (up to 8.9 GPa), with the values derived from NaCl gauge. Based on Brown's 1999 EOS find bulk modulus ${B}_{0}=41.2(2)$ GPa at 298 K increase by $14%$ ${B}_{0}$ = 47.0(5) 80 K. The ambient value coincides within 0.35 (1.7%) determined published ultrasonic data. good agreement between neutron deteriorates if are Decker's...

First-principles calculations are employed to study ${\mathrm{SrTiO}}_{3}(001)$ $(1\ifmmode\times\else\texttimes\fi{}1)$ surfaces with both SrO and ${\mathrm{TiO}}_{2}$ termination. A detailed geometry of the relaxed systems, surface energy, individual relaxation energies two types obtained. The longitudinal dipole moments derived from variation macroscopic electrostatic potential along normal direction. Pseudopotential--plane-wave performed in slab geometry, on symmetric asymmetric slabs;...

A quantitative study of the structure and electronic properties Co-corrole, Co-corrin, Co-porphyrin, using density functional theory, is reported. The each macrocycle optimized, with no symmetry constraints, by considering different spin states. ground-state structures states (S = 1 for S 0 Co-corrin 1/2 Co-porphyrin) are in good agreement experimental data available. trends sizes coordination cavities upon varying inner metal atom and/or analyzed compared those Fe-porphyrin we studied...

The pressure-volume relationship and the zone-center optical-phonon frequency of cubic diamond at pressures up to 600 GPa have been calculated based on density-functional theory within local-density approximation generalized gradient approximation. Three different approaches, viz. a pseudopotential method applied in basis plane waves, an all-electron relying augmented waves plus local orbitals, intermediate approach implemented projector used. All these methods approximations yield...

Methods for the theoretical prediction of static equilibrium properties solids by means total-energy minimisation are investigated. The authors discuss practical aspects and pitfalls connected with finite plane-wave basis sets, show how a number ambiguities can be overcome aid stress theorem. procedures developed very efficient achieving full convergence calculated properties. Precautions necessary when performing calculations that not fully converged, which unavoidable complex systems, discussed.

The local density functional technique is applied to the ab initio calculation of ground-state properties cubic silicon carbide. Norm-conserving pseudopotentials are used with atomic numbers elements as only inputs. Results for equation state, real-space distribution electronic charge and selected phonons presented. pressure derivative bulk modulus, B'0, predicted Gruneisen parameters describing variation phonon modes calculated. More than 1000 plane waves per unit cell needed achieve...