ATOM POSITIONS FROM HYPERFINE DATA FOR GERMANIUM CENTERS IN ALPHA-QUARTZ

Germanium 3+ occurs in alpha-quartz substitutionally for silicon 4+, e ither as complex anions \GeO4\(-) or these anions charge-compensated w ith interstitial alkali cations, i.e., as two primary types of species denoted by \GeO4/M\(O)(A,C), where M = Li, Na, A brief review of the relevant literature is presented, Using the molecular-orbital spin pop ulation for the unpaired electron in each center, available from Ge-73 and O-17 hyperfine data, an evaluation of the likely M(+) positions w ithin the quartz structure has been performed, In part, the present ca lculations were done to test the well known McConnell-Strathdee approa ch with well defined experimental hyperfine data, A generalized discus sion of atom-position determination by EPR, and problems encountered i n the process, is included.