Mina Talati

Shape and Size Dependent Melting Point Temperature of Nanoparticles

The present paper reports a simple calculation of the size and shape dependent melting temperature of nanoparticles. The melting temperature of any nanoparticle basically depends on the ratio of surface atoms to the total atoms. Significant melting temperature suppression is observed when the particle size approaches the sub-20 nm range. The behavior of melting temperature is similar for the larger nanoparticles of all considered shapes but differs significantly for small nanoparticles. Different melting temperature is predicted for the nanoparticles of the same size in different shapes.

Atomistic simulations of elastic and plastic properties in amorphous silicon

We present here potential-dependent mechanical properties of amorphous silicon studied through molecular dynamics (MD) at low temperature. On average, the localization of elementary plastic events and the co-ordination defect sites appears to be correlated. For Tersoff potential and SW potential the plastic events centered on defect sites prefer 5-fold defect sites, while for modified Stillinger-Weber potential such plastic events choose 3-fold defect sites. We also analyze the non-affine displacement field in amorphous silicon obtained for different shear regime. The non-affine displacement field localizes when plastic events occur and shows elementary shear band formation at higher shear strains.

Theoretical study of the transverse acoustic phonons of GaSb at high pressure

We have investigated the phonon dispersion curves and one-phonon density of states up to the pressure of 8 GPa using a theoretical model, namely the rigid ion model. The transverse acoustic phonons as a function of pressure have been compared with the recently measured inelastic neutron scattering data which show a strong softening near the zone boundaries. The calculated one-phonon density of states show pronounced shift in the peak positions with the increase in pressure.

STRUCTURAL PHASE TRANSITION IN BORON COMPOUNDS AT HIGH PRESSURE

The high-pressure induced structural phase transitions and pressure induced elastic and anharmonic behavior of boron compounds viz. BN, BP, and BAs have been investigated using an inter-ionic potential approach based on charge transfer effect. These compounds go to NaCl phase (B1) under pressure from zinc blende phase (B3). The variations of second-order elastic constants and their combinations follow a systematic trend with pressure, identical to that observed in other compounds of zinc blende structure family. Shear stiffness constants decrease with increasing pressure up to phase transition pressure. The bulk moduli of these compounds are in reasonably good agreement with other theoretical and experimental data. The values of phase transition pressure of these compounds obtained by using the present approach are also in good agreement with those predicted by using the pseudo potential approach. The present approach has also succeeded in predicting the Born and relative stability criterion for stable zinc blende phase of these compounds. We also present a set of third-order elastic constants and pressure derivatives of second-order elastic constants for boron compounds.