R. Balzer

Gitterfehlordnung in KCl mit Farbzentren

AbstractColor centers were created in KCl single crystals by additive coloration and X-irradiation at room temperature. Change of lattice parameter was determined by an X-ray method and change of mass density by a hydrostatic flotation method. Combination of these results, together with optical absorption measurements, led to the following results: F centers in additively colored KCl are Schottky defects. They cause a lattice expansionΔ v/v=0.58 perF center.F centers in X-irradiated KCl are parts of Frenkel defects. During irradiation atoms are displaced to interstitial lattice sites. The volume expansion isΔ v/v=1,15 perF center.

Determination of the structure of the self-interstitial atom in solid argon from diffuse X-ray scattering

The diffuse X-ray intensity scattered from the displacement field of point defects in low-temperature X-irradiated argon crystals is measured. The double force tensor describing the long-range distortion field of the interstitial atom is derived from absolute intensities together with the relative lattice parameter change. The experimental results are compared with theory. This symmetry of the defect, as determined from experimental data, is in accordance with the (100) split interstitial as well as with defects with cubic symmetry, i.e. the (110) crowdion and the (110) and (111) dumb-bells can be excluded. The formation volume is found to be 0.9 atomic volumes.

Evidence for Frenkel defect formation in low-temperature X-irradiated KCl and KBr

Abstract Combined measurements of lattice parameter and macroscopic length change give evidence that Frenkel defects are created in KCl and KBr during X-irradiation at 8°K.

Measurement of stored energy of KBr after X-irradiation at low temperature

The release of stored energy of X-irradiated KBr measured between 10 and 50K. A very sensitive heat flow calorimeter is described, which allows the detection of energy release rates as small as 0.5% of the heat capacity of the sample. The observed annealing stages of stored energy are compared with lattice parameter, length change, and optical absorption measurements from similar annealing experiments. The energy release can be identified as due to recombination of Frenkel pairs. The stored energy per Frenkel pair was obtained in KBr by combined measurements of the energy release and the change of optical absorption while warming up an irradiated crystal. For the alpha +I Frenkel pair a value of (4.0+or-0.8) eV was found. For the recombination of an F+H Frenkel pair an energy release of (2.7+or-0.6) eV was obtained.

Change of crystal dimensions due to the alignment of anisotropic elastic dipoles

Abstract A method is proposed to determine the elastic dipole tensor of a lattice defect. The length change of a crystal was measured, when the defect orientation in the lattice is changed.