High pressure and temperature effects on the molecular crystal 2-amino-5-methyl-1,3,4-thiadiazole

Author(s)

de Toledo, Thiago A. ^[1] ; Bento, Ricardo R. F. ^[1] ; Cunha, Thiago R. ^[2] ; Pizani, Paulo S. ^[2]

Affiliation

^[1] Univ Fed Mato Grosso, Inst Fis, BR-78060900 Cuiaba, Mato Grosso - Brazil

^[2] Univ Fed Sao Carlos, Dept Fis, Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: Journal of Raman Spectroscopy; v. 49, n. 10, p. 1713-1721, OCT 2018.
• Web of Science Citations: 1

Abstract

We report a detailed study of 2-amino-5-methyl-1,3,4-thiadiazole (C3H5N3S) using Raman and infrared spectroscopy techniques combined with density functional theory at the condensed phase and for the isolated molecule in gas phase. This information provides the vibrational mode assignments, which will give a basis for the better understanding of the changes in the Raman spectra due to the temperature (from 10 to 413K) and pressure (up to 9.2GPa at room temperature) variation. The anharmonic effects in the Raman spectra of C3H5N3S were identified in the temperature range 10-393K, corresponding to wavenumber shift, changes in the line intensity, and linewidth. The crystal undergoes to phase transition in the temperature range 403-413K, as indicated by the discontinuity in the d/dT of several Raman bands in external and internal mode region. As pressure increases, a notable change in the Raman spectra occurs at 1.6GPa, suggesting a second-order phase transition attributed to splitting, discontinuity in the d/dP, and red shift of the external and internal Raman modes. All changes in the Raman spectrum were reversible after releasing pressure. (AU)

• FAPESP's process: 13/07793-6 - CEPIV - Center for Teaching, Research and Innovation in Glass
• Grantee: Edgar Dutra Zanotto
• Support type: Research Grants - Research, Innovation and Dissemination Centers - RIDC