The second-order elastic constants of AgBrAgCl mixed crystals from 77 to 300 K

Abstract

The three independent second-order elastic constants of four mixed AgBrAgCl single crystals have been measured from room temperature down to liquid nitrogen temperature. The single crystals, with 19.5, 39.1, 56.6 and 78.7 mol % AgCl, had (110) axes. The increase in each elastic constant over this temperature range is almost identical in each mixed crystal. The measured longitudinal constant C' 11 = ( C 11 + C 12 + 2 C 44)/2 increases by about 17%, the shear constant C 44 increases by about 10%, and the shear constant C 11 = ( C 11 − C 12)/2 increases by about 48%. The measured bulk modulus B = ( C 11 +2 C 12)/3 increases by about 15% as the lattice becomes stiffer. The changes in the elastic constants are basically linear down to approx. 150 K, where the temperature derivatives begin to decrease in magnitude. The deviation from the Cauchy relation, C 12 = C 44, remains constant in each mixed crystal as the temperature decreases. The anisotropy, C ' C 44, however, increases by about 33% in each crystal as the temperature decreases.