THERMAL-EXPANSION AND GRUNEISEN PARAMETERS OF AMORPHOUS-SILICON - A REALISTIC MODEL CALCULATION

Using a realistic model, the mode Gruneisen parameters gamma and the t emperature dependent coefficient of linear thermal expansion alpha(T) are calculated for amorphous silicon. The resulting gamma values diffe r 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 de pendent.