The coefficient of bond thermal expansion measured by extended x-ray absorption fine structure

摘要

The bond thermal expansion is in principle different from the lattice expansion and can be measured by correlation sensitive probes such as extended x-ray absorption fine structure (EXAFS) and diffuse scattering. The temperature dependence of the coefficient alpha(bond)(T) of bond thermal expansion has been obtained from EXAFS for CdTe and for Cu. A coefficient alpha(tens)(T) of negative expansion due to tension effects has been calculated from the comparison of bond and lattice expansions. Negative lattice expansion is present in temperature intervals where alpha(bond) prevails over alpha(tens); this real-space approach is complementary but not equivalent to the Gruneisen theory. The relevance of taking into account the asymmetry of the nearest-neighbours distribution of distances in order to get reliable bond expansion values and the physical meaning of the third cumulant are thoroughly discussed. (C) 2014 AIP Publishing LLC.