Improvement of the spin-polarized self-consistent-charge extended Hückel tight-binding method

The spin-polarized self-consistent-charge extended Hückel tight-binding (SP-SCC-XHTB) method has been developed by authors to study the electronic structures of rutile-type transition metal dioxides, MO2, with both the nonmagnetic and magnetic phases. This method has been used to successfully predict the electronic structures of nonmagnetic (n) MO2’s with M =Ti, V, Nb, Ta, Cr and ferromagnetic (f) CrO2, but is inadequate to predict the value of the energy gap of a semiconductive n-MnO2. The SP-SCC-XHTB band structure calculation, which includes all the relativistic effects in a first principal manner, has only one empirical parameter on the evaluation of the matrix elements of the non-relativistic Hamiltonian H0. In this paper, the SP-SCC-XHTB method is improved so as to evaluate the matrix elements of the H0 in a more appropriate manner. The band structure calculations are carried out for the n-MO2’s with M =Ti, V, Nb, Ta, Cr and Mn, the f-CrO2 and the af-MnO2. With the improvement it is shown that the SP-SCC-IXHTB band structure calculations give reasonable results for the electronic structures of all the MO2’s considered in the present paper.