ANHARMONICITY OF PLATINUM UNDER HP AND HT

Abstract

In order to examine the pressure effect on anharmonic thermal vibrations of Pt, Extended X-ray Absorption Fine Structure (EXAFS) spectra near Pt K-edge and L₃-edge were measured in the temperature range from 300 to 800 K under pressures up to 6GPa, using large volume high-pressure devices and synchrotron radiation. We have investigated the anharmonic interatomic potentials by a cumulant expansion method. The values of EXAFS Debye-Waller factors, σ2 and σ3, become smaller with increase of pressure. The anharmonic effective pair potential V(u) =(1/2!)au ² +(1/3!)bu ³ was evaluated and the potential coefficient a at 0.1 MPa and 6GPa are 4.8 and 5.0eV/Ų, respectively. The anharmonic potential parameter b decreases with increasing pressure.

Keywords:

• High-pressure
• High-temperature
• Anharmonicity
• Platinum
• EXAFS