Local thermal expansion in copper: extended x-ray-absorption fine-structure measurements and path-integral Monte Carlo calculations.

A combined approach has been used to study thermal effects on the extended x-ray absorption fine-structure (EXAFS) of copper between 4 and 500 K. A phenomenological data analysis shows that the thermal expansions measured from the first and third cumulants significantly differ between each other and from the crystallographic thermal expansion. Path-integral Monte Carlo calculations of EXAFS cumulants have been performed, using a many-body potential. The good reproduction of experimental values validates the phenomenological analysis and opens more perspectives for applications to more complex systems. It is shown that the reproduction of EXAFS parameters allows for a test of the interaction potentials with regard to anharmonicity.