Thermal expansion and Gruneisen parameters of amorphous silicon: A realistic model calculation

Using a realistic model, the mode Gruneisen parameters gamma and the temperature dependent coefficient of linear thermal expansion alpha(T) are calculated for amorphous silicon. The resulting gamma values differ from the crystalline case in having all diversity suppressed, except for a minority of high-frequency localized and low-frequency resonant modes. The latter have very large, mostly negative gamma (up to -31), caused by volume-driven internal strain. As a result, the values for alpha(T) are lower than those of crystalline silicon and are sample dependent.