The vibrational spectra of phosphorous oxynitride at high pressures

The infrared and Raman spectra of phosphorous oxynitride PON, a homologue of silica, have been measured at pressures up to 23 Gpa. The moganite and the α-quartz type crystalline forms of PON have been studied. A correlation has been established between the spectra of PON and those of silica. In the moganite type PON a phase transition has been observed at ≈ 4 Gpa. Some preliminary results of an ab initio molecular dynamics simulation are discussed.