Thermal Expansion and Gruneisen Parameters of Amorphous Silicon: A Realistic Model Calculation

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