Accurate and transferable extended Huckel-type tight-binding parameters

We show how the simple extended Huckel. theory can be easily parametrized i n order to yield accurate band structures for bulk materials, while the res ulting optimized atomic orbital basis sets present good transferability pro perties. The number of parameters involved is exceedingly small, typically ten or eleven per structural phase. We apply the method to almost fifty ele mental and compound bulk phases.