We have calculated the melting temperature of tungsten by two ab initio approaches. The first approach can be divided into two steps. In the first step, we simulate a large coexisting solid and liquid system by the classical embedded-atom method potential and obtain an approximate melting temperature. In the second step, we compute the accurate melting temperature by performing the ab initio fr...

Common methods of determining atomic polarizabilities suffer from the inclusion of nonlocal effects such as charge polarization. A new method is described for determining fully ab initio atomic polarizabilities based on calculating the response of atomic multipoles to the local electrostatic potential. The localized atomic polarizabilities are then used to calculate induction energies that are ...

Results of detailed calculations for SrTiOs (100) surface relaxation and the electronic structure for the two different terminations (SrO and TiO2) are discussed. These are based on ab initio Hartree-Fock (HF) method with electron correlation corrections and Density Functional Theory (DFT) with different exchange-correlation functionals, including hybrid (B3PW, B3LYP) exchange techniques. Resul...

We extend the effective fragment molecular orbital method (EFMO) into treating fragments connected by covalent bonds. The accuracy of EFMO is compared to FMO and conventional ab initio electronic structure methods for polypeptides including proteins. Errors in energy for RHF and MP2 are within 2 kcal/mol for neutral polypeptides and 6 kcal/mol for charged polypeptides similar to FMO but obtaine...

A globally accurate many-body expansion potential energy surface is reported for HCS(X2A') by fitting a wealth of accurate ab initio energies calculated at the multireference configuration interaction level using aug-cc-pVQZ and aug-cc-pV5Z basis sets via extrapolation to the complete basis set limit. The topographical features of the present potential energy surface are examined in detail and ...

Ab initio simulations aimed at modelling and interpreting STM induced molecular isomerization of naphthalocyanine molecule are presented. Free energy profile, reaction path and activation energies were obtained using the metadynamics method in the frame of Car-Parrinello Molecular Dynamics (CPMD). We propose a multiscale model of the molecular switch process, based on the Ehrenfest Molecular Dy...

This thesis presents an ab initio study of biological molecules using first-principles molecular dynamics. Density functional theory and Car-Parrinello molecular dynamics are used in the computational modeling of the water molecules and the amyloidforming peptide GNNQQNY derived from the yeast prion protein Sup35. The Young's modulus of the fibril obtained from the ab initio method is larger th...