Structural Properties of Amorphous Geo2: A Molecular Dynamics Simulation Studies

Abstract

Understanding the structural properties of network-forming glasses is of great interest not only in condensed matter physics, geoscience, and materials science, but also in engineering and industry. Experimental results suggest that amorphous germanium oxide have a tetrahedral local structure that serves as a corner-sharing building block to produce a three-dimensional network. However, it is very challenging to experimentally deduce the medium (or intermediate) range order. In this study, the structural properties of amorphous germanium oxide was investigated by means of the classical molecular dynamics technique. The simulations were done in the microcanonical ensemble, with a system at a density of 3.7 g cm -3 , using a pairwise potential. The pair correlation functions, bond angle and coordination numbers are computed. The simulation results show that there exists a short range order, defined by the nearest neighborhood of a Ge atom, which consists of a Ge(O1/2)4 tetrahedron, with a Ge-O bond length of 1.75 A, longer than the Si-O bond length (1.62 A). Beyond this basic unit, the tetrahedra are linked to each other by their vertices, forming an angle Ge-O-Ge of ∼130•, but randomly distributed in the space.