Stability Of Diamond Research Articles

Ustoichivost' almaza pri vysokikh davleniyakh

Ustoichivost' almaza pri vysokikh davleniyakh

On the tetragonal β-Sn-type structure as the high-pressure phase

A high-pressure Cs IV phase of alkali metals is equivalent to the beta -Sn(II) structure predicted previously. At higher pressures, the beta -Sn(II) phase tends to become more stable than beta -Sn(i), which corresponds to the well known beta -Sn-type structure as a high-pressure phase of diamond-type structure. Numerical calculations of the relative stability of diamond or zinc-blende, beta -Sn(I) and beta -Sn(II) structures are performed for Si and GaSb, and of BCC, FCC, beta -Sn(I) and beta -Sn(II) structures for Rb and Cs using a perturbational treatment based on the pseudopotential formalism. Numerical results for the transition pressure, relative volume, volume discontinuity and transition heat are then discussed together with the observed data.

Diamond structure versus wurtzite structure for silicon

A calculation of the total energy of silicon in crystal structures with tetrahedral coordination is self-consistently performed in a localised scheme. The behaviour of the total energy is similar to the one obtained with a rather sophisticated pseudopotential within a very different computational framework. We show that the change in the electrostatic energy is dominant over the remainder contributions, which makes it responsible for the stability of diamond with respect to wurtzite structure. Both the band structure and the interaction between Wannier functions are reported as well.