Vibration problem of H in silicon

A large discrepancy in the calculated frequency of Si–H bond in Si is found between the frozen-phonon calculation and molecular dynamic simulation. Differently from the frozen-phonon calculation, in which a linear chain structure Si–H–Si is assumed, the bond Si–H–Si is actually bending at finite temperatures. The H is rotating around the bond axis. On the average, H is observed as it were at the bond center. LDA calculation overestimates the bond length. The above two errors are cancelled out in the frozen-phonon calculation.