THE 2ND-ORDER ELASTIC-CONSTANTS OF AGBR FROM 77-K TO 300-K

The three independent second-order elastic constants of AgBr have been measured from room temperature down to liquid nitrogen temperature. A single crystal with a (110) axis was used for the measurements. The measured longitudinal elastic constant C prime //1//1 equals (C//1//1 plus C//1//2 plus 2C//4//4)/2 increases by 16% over this temperature range. The elastic shear constant C//4//4 increases by almost 11%, while the elastic shear constant C prime equals (C//1//1 minus C//1//2)/2 increases by 50% over this range. The measured bulk modulus B equals (C//1//1 plus 2C//1//2)/3 increases by almost 15% as the lattice becomes stiffer. The initial temperature derivatives of the elastic constants are similar to those previously measured. The changes in the elastic constants are basically linear down to approximately 150 K, where the temperature derivatives begin to decrease in magnitude. These results are similar to those previously obtained for AgCl.