Best Localized Symmetry‐Adapted Wannier Functions of the Diamond Structure

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Abstract
By application of proper unitary matrices the four Bloch functions of each bandgroup with equal wave vector k are transformed into modified Bloch functions in such a way that the resulting four sets of Wannier functions are adapted to the tetrahedral symmetry of the lattice. The Wannier functions behave like the “equivalent MO's” of the tight‐binding approximation (but with vanishing non‐orthogonality integrals). Furthermore, we give explicitely those phases of the Bloch functions that lead to best localized Wannier functions. Values of energy matrix elements between these functions are determined for Ge and Si.