Vibrational spectra and analysis on the molecule of potassium pentaborate crystal (KB5)

Abstract

161-166<span style="font-size: 16.0pt;mso-bidi-font-size:9.0pt;font-family:" times="" new="" roman","serif""="">Potassium pentaborate (KB5) crystals have been grown by solution growth technique. A structural investigation on the KBS crystal is made, using FTIR and laser Raman spectra. The molecular structure of KBS belongs to C2v symmetry considering the hydroxyl group as point mass. The total number of normal modes of vibration is 39 and are distributed as Γvib= 14A1<span style="font-size:12.5pt;mso-bidi-font-size:5.5pt; font-family:" arial","sans-serif""=""> <span style="font-size:16.0pt; mso-bidi-font-size:9.0pt;font-family:" arial","sans-serif""="">+ 5A2 <span style="font-size:16.0pt;mso-bidi-font-size:9.0pt;font-family: " arial","sans-serif""="">+ 10B1<span style="font-size:12.5pt; mso-bidi-font-size:5.5pt;font-family:" arial","sans-serif""=""> + 10B<span style="font-size:12.5pt;mso-bidi-font-size:5.5pt; font-family:" arial","sans-serif""="">2<span style="font-size:12.5pt; mso-bidi-font-size:5.5pt;font-family:" arial","sans-serif""="">. A normal coordinate analysis has been carried out with an orthonormal set of symmetry coordinates following Wilson F-G matrix method. The potential constants evaluated for this molecule are found to be in good agreement with literature, thereby, confirming the vibrational assignments. To check whether the chosen set of vibrational frequencies contributes maximum to the potential energy associated with the normal coordinates of the molecule, the potential energy distribution has been evaluated. Further, the thermogravimetric analysis (TGA) confirms the decomposition of KBS taking place in two stages. The differential scanning calorimetry (DSC) curve of KBS crystals has been recorded in the temperature range 50-580 °C. The phase transition temperature and enthalpies of KBS were measured and the results are discussed. </span