Structure and dynamics of alkali borate glasses: a molecular dynamics study

• Published in: Journal of non-crystalline solids 1995-03, Vol.182 (3), p.235-247
• Main Authors: Verhoef, A.H., den Hartog, H.W.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Disordered solids; Exact sciences and technology; Glasses; Infrared and raman spectra and scattering; Lattice dynamics; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Physics; Structure of solids and liquids; crystallography; Vibrational states in disordered systems
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/0022-3093(94)00554-0

Structural and dynamical properties of lithium, cesium and mixed alkali (i.e., lithium and cesium) borate glasses have been studied by the molecular dynamics method. The calculations yield glass structures consisting of planar BO 3 triangles and BO 4 tetrahedrons with no sixfold ring structures at all. Alkali ions show a strong preference to reside in the vicinity of non-bridging oxygen atoms, a tendency which is stronger for lithium ions than for cesium ions. The experimental Raman peaks at 805 and 770 cm −1 are reproduced by symmetric breathing modes of BO 3 and BO 4 units, respectively. Simulated infrared absorption spectra reproduce the experimental spectra quite well. It appears that the velocities of different cesium ions show much more correlation than those of the lithium ions and that the frequency spectra of Li + and Cs + ions are in good agreement with far-infrared measurements.