Results of full-potential linear muffin-tin orbital generalized gradient approximation calculations of the band structure and boron electric field gradients (EFG’s) for the new medium-(formula presented) superconductor (formula presented) and related diborides (formula presented) (formula presented) Al, Sc, Ti, V, Cr, Mo, and Ta are reported. The boron EFG variations are found to be related to specific features of their band structure and particularly to the (formula presented) hybridization. The strong charge anisotropy at the B site in (formula presented) is completely defined by the valence electrons-a property which sets (formula presented) apart from other diborides. The boron EFG in (formula presented) is weakly dependent on applied pressure: the B p-electron anisotropy increases with pressure, but it is partly compensated by the increase of core charge asymmetry. The concentration of holes in bonding σ bands is found to decrease slightly from 0.067 to 0.062 holes/B under a pressure of 10 GPa. Despite a small decrease of (formula presented) the Hopfield parameter increases with pressure and we believe that the main reason for the reduction under pressure of the superconducting transition temperature (formula presented) is the strong pressure dependence of phonon frequencies, which is sufficient to compensate for the electronic effects.
|Number of pages||4|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2002|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics