Electric field gradients have been measured at substitutional lattice sites
in ternary semiconductors using Perturbed gamma-gamma Angular Correlation
spectroscopy (PAC). The experimental results for A(I)B(III)C(2)(VI) chalcop
yrite structure compounds and square A(II)B(2)(III)C(4)(VI) defect chalcopy
rites are compared with ab-initio calculations. The latter were carried out
with the WIEN code that uses the Full Potential Linearized Augmented Plane
Wave method within a density functional theory. The agreement between expe
riment and theory is in most cases very good. Furthermore, the anion displa
cements in AgGaX2-compounds (X: S, Se, Te) have been determined theoretical
ly by determining the minimum of the total energy of the electrons in an el
ementary cell.