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

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 a density of 3.7gcm^-3, using a pairwise potential. The resulting neutron static structure factor is compared to 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(O_1/2)₄ tetrahedron. Beyond that, there is an intermediate range order composed of 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.