Thermal Expansivity Related to the Frequency Shifts for the I-II Phase Transition In Ammonium Iodide


YURTSEVEN H. H. , Erdogan M. K.

2nd International Conference on Perspectives in Vibrational Spectroscopy, Thiruvananthapuram, Hindistan, 24 - 28 Şubat 2008, cilt.1075, ss.215-217 identifier identifier

  • Cilt numarası: 1075
  • Basıldığı Şehir: Thiruvananthapuram
  • Basıldığı Ülke: Hindistan
  • Sayfa Sayıları: ss.215-217

Özet

We calculate here the temperature dependence of the frequency shifts (1/v)/(partial derivative v/partial derivative P)(T) for the v (125 cm(-1)) Raman mode of NH(4)I close to the I-II phase transition (T(c)=257 K). For this calculation the lattice parameter data for NH(4)I is used. We establish the Pippard relation in terms of the spectroscopic parameters by correlating the thermal expansivity alpha(P) with the frequency shifts (1/v)/(partial derivative v/partial derivative P)(T) through the mode Gruneisen parameter of the v (125 cm(-1)) mode for the I-II phase transition in NH(4)I. From a linear variation of alpha(P) with the (1/v)/(partial derivative v/partial derivative P)(T) for the v (125 cm(-1)) Raman mode according to the Pippard relation, we extract the slope value of dP/dT=18.9 bar/K, which agrees with the observed value for the I-II phase transition in a P-T phase diagram of NH(4)I.