Thermal expansion and interatomic potentials of silver revealed by extended x-ray absorption fine structure spectroscopy using high-order perturbation theory

Abstract

Extended x-ray absorption fine structure investigations are reported concerning the thermal expansion behavior of silver in a wide range of temperatures from 10 to about 950 K as measured in the transmission mode. Models based on the quantum and classical thermodynamic perturbation theory are used to interpret the experimental data and compared to x-ray diffraction results of the crystalline silver material. To this aim, the third- and fourth-order perturbation formulas of the cumulants and of the thermal expansion coefficient have been developed by means of the quantum-statistical theory and are presented here. By using these formulas, the thermal expansion of silver bonds can be described by the temperature-dependent first cumulants as well as by an anharmonic potential function in correlation with the cumulant expansion in the complete range of temperatures.