The pressure dependence of the average interatomic distances for the first Ga shell in bulk tetrahedral a-GaSb has been studied by Ga K-edge extended x-ray-absorption fine structure. We have found that the microscopic compressibility of the covalent bonds in the disordered network is less than in the crystalline zinc-blende structure. Comparison of the microscopic bond-bulk modulus (Bbond≈ 105±20 GPa) in a-GaSb with the macroscopic bulk modulus (Bcr= 35 GPa) and with the bulk modulus of c-GaSb (Bcr= 56 GPa) gives unambiguous evidence for a pressure-induced geometrical or topological distortion in the a-GaSb tetrahedral network. Physical reasons for the observed behavior of volume in the amorphous tetrahedral network under pressure, such as a bond-bending distortion mechanism and a nonlinear averaging for a system with heterogeneous compressibility, are discussed.
|Journal||Physical Review B: Condensed Matter and Materials Physics|
|Publication status||Published - 15 Nov 1996|