Structural and vibrational properties of amorphous GeO2: a molecular dynamics study

Abstract

We studied the structural and dynamical properties of amorphous germanium oxide (GeO2) by means of the molecular dynamics technique. The simulations were done in the microcanonical ensemble, with a system at density of 3.7 g/cm3, using a pairwise potential. The resulting neutron static structure factor agree very well with experimental results. The network topology of our system is analyzed through partial pair correlations, coordination number and angle distributions. A detailed analysis of the interatomic distances reveals that in the amorphous state there is a short-range order dominated by a slightly distorted Ge(O1/2)4 tetrahedron. Beyond that, there is an intermediate range order composed by vertex-sharing tetrahedra. The vibrational properties were characterized by means of the density of states, obtained as a Fourier transform of the velocity autocorrelation function. The vibrational density of states has two bands, a low frequency one related to the inter-tetrahedron vibration and a high frequency band related to the intra-tetrahedron vibration.