Incommensurate transition effect on a molecular Raman band in thiourea (SC(NH2)2) crystal

Abstract

A molecular Raman band of thiourea (SC(NH2)2) crystal was studied as a function of temperature through the incommensurate and ferroelectric phases. The temperature-dependent splitting Delta nu of the molecular Raman band at 625 cm-1, corresponding to a pi (SCN) deformation mode of Ag symmetry in the paraelectric phase, was found to be best fitted by Delta (nu2) varies as (T'I-T)0.54 below the incommensurate transition temperature TI.