Structural and vibrational properties of Si clathrates in a generalized tight-binding molecular-dynamics scheme

The structural and vibrational properties of Si in two fourfold coordinated crystalline structures (clathrates) are studied and compared with those in the diamond structure using a generalized tight-binding molecular-dynamics scheme. The vibrational spectra reported for both clathrates are obtained using quantum methods and contain many interesting features, the most striking being the presence of a gap. Additionally, theoretical Raman spectra for these clathrates are also presented.