A theoretical study of liquid and glassy GeSe(2

We present results of an ab initio molecular dynamics study of glassy GeSe$sb2$ using a 216 atom model. The network topology of our model has been analyzed through partial pair correlation functions, angle distributions, partial static structure factors, and ring structures. The total static structure factor and first sharp diffraction peak are in good agreement with experiment. The vibrational density of states (VDOS) and dynamical structure factor are in good agreement with experimental results as well. We have visualized the normal mode vectors in order to qualitatively understand their motion. The electronic density of states compares very well with experimental UPS and XPS measurements. The localization of the electronic states has been analyzed as well.;The structural, vibrational, and electronic properties of liquid GeSe$sb2$ are investigated using ab initio molecular dynamics. The static structure factor S(Q) and the pair correlation functions of our model are in good agreement with experiment. We find many similarities between the topology of the liquid and the glass state. In addition we introduce a new way of characterizing the intermediate range order of liquid and glassy GeSe$sb2$ through fourfold and sixfold rings. The overall vibrational density of states is found to be consistent with Raman experiments. The intensity of the low frequency modes, splitting of the A$sb1$ and A$sb{1c}$ peaks, and the decrease in the intensity of the high frequency modes are all reproduced. The electronic density of states has been determined and compared to our results for glassy GeSe$sb2$. We find that an increase in Se bond length and bond angle disorder significantly broadens the conduction band. The time dependent behavior of the electronic eigenvalues has been examined and transient events have been observed in which an electronic state crosses the optical gap. The structural configurations which produce states in the optical gap have been determined for the first time using an ab initio molecular dynamics approach. These results are in agreement with experimental photoluminescence and electron spin resonance data. We also find that a linear relationship exists between the root mean square of the thermal fluctuations of an electronic eigenvalue in time and its localization.