In this work, we have calculated ab initio the equation of state, the principal phonon modes, the effective charges and the temperature dependence of the specific heat for the III-Nitrides, by using the density-functional theory within the local density approximation, plane wave expansions and the pseudopotential method. A good agreement with the experiment and other calculations is obtained, w...

Among the experimentally observed structures of molecular C36, our calculations show that the structure with D6h symmetry is one of the two most energetically favorable. Based on this result and the fact that D6h is conducive to forming a periodic system, we propose a new solid phase of carbon using C36 fullerenes as a basis. Full structural relaxations and electronic density of states are eval...

The zone-center phonons are calculated for yellow phase CsSnI3 using density functional perturbation theory in a plane-wave pseudopotential method. The infrared absorption and reflection spectra are simulated and show that the absorption has a strong contribution from the LO as well as TO modes. The polarization-dependent Raman spectra for various configurations are simulated. The results for t...

Motivated by possible astrophysical and biological applications we calculate visible and near UV spectral lines of proflavine (C13H11N3, 3,6-diaminoacridine) in vacuum, as well as its anion, cation, and dication. The pseudopotential density functional and time-dependent density functional methods are used. We find a good agreement in spectral line positions calculated by two real-time propagati...

A comparison between experimental and theoretical electron energy loss near edge structure ~ELNES! of B and N K edges in cubic boron nitride is presented. The electron energy loss spectra of cubic boron nitride particles were measured using a scanning transmission electron microscope. The theoretical calculation of the ELNES was performed within the framework of density functional theory includ...

The structure and properties of vacancies in a 2 nm Si nano-crystal are studied using a real space density functional theory/pseudopotential method. It is observed that a vacancy’s electronic properties and energy of formation are directly related to the local symmetry of the vacancy site. The formation energy for vacancies and Frenkel pair are calculated. It is found that both defects have low...

Using the atomistic pseudopotential method complemented by configuration interaction calculations, we have studied the electronic and optical properties of ZnO nanowires (NWs) in the presence of quantum confinement effects. Our results indicate that the near-band-edge exciton experiences a crossover from an in-plane polarized A-exciton (for D≥ 3 nm) to an out-of-plane polarized C-exciton (for D...

Spectroscopic properties of dimers, hydrides, oxides, fluorides and sulphides of the elements In, Sn and Sb have been calculated using energy-adjusted pseudopotentials. Results are given for bond lengths R e, dissociation energies D e, vibrational frequencies co e and dipole moments #e of the ground states. Comparison is made both with experimental and theoretical values, where available. The i...