Transformation strain by chemical disordering in silicon carbide

Swelling is observed in radiation-induced amorphization of SiC, which can be attributed to both structural and chemical disordering. By first-principles calculations, an attempt is made to separate the two factors by creating complete chemical disorder with no initial structural disorder in a 64-atom supercell. By relaxing all stresses and internal forces, significant transformation strains, both hydrostatic and shear, are observed. The relaxed configurations are found to be metallic. Softening of the bulk modulus is found to correlate closely with volume expansion, regardless of whether the expansion is caused by structural or chemical disordering, or with no disorder at all. It is postulated that partial chemical disordering contributes significantly to the internal residual stresses and macroscopic swelling of amorphous SiC. (C) 2004 American Institute of Physics.