Recent studies on the crystal structure, electronic structure and mechanical properties of noble metal nitrides

Platinum nitride was the first noble metal binary nitride to be synthesized in crystal form under high pressure and high temperature. It has stimulated many theoretical studies on account of its abnormally high bulk modulus of about 372 GPa and intriguing electronic properties. Although X－ray diffraction can determine the position of the Pt atom, the much smaller mass of N makes it impossible to determine the exact positions of the N atoms. By means of Raman－scattering the symmetry of the N atoms can be confined, but their exact positions are still unclear. Therefore, investigations have mostly focused on determining the crystal structure of the Pt-N system, and have opened a new area of high－pressure research: the synthesis and characterization of noble metal nitrides under high pressure.