Expanded fluid mercury in the metal-nonmetal transition range. An ab-initio MD study
Fluid Hg undergoes a metal-nonmetal (M-NM) transition when is expanded from the triple point towards a density of around 9 gr/cm3 at high temperature and high pressure. To investigate the related changes in the static and dynamic properties, we have performed ab-initio molecular dynamics simulations for some states close to the M-NM transition range. The calculated static and dynamic structure factors show a good agreement with the available experimental data. It is found that the volume expansion reduces the number of nearest neighbors at the expense of the inner ones. The dispersion relation exhibits a positive dispersion which is not so marked as that deduced from experimental data. The total electronic density of states shows the appearance of a band gap at a density somewhat smaller than 9 gr/cm3.
The experimental bias dependence of the power output spectrum from various types of HEMT at large signal excitation was studied and compared with predicted values obtained from a newly proposed HEMT model. Good agreement between simulated and measured power spectrum up to at least the fourth harmonic was demonstrated for HEMT devices from different manufacturers. An extension of the existing model is also proposed, which models the V/sub ds/ dependence of the transconductance peak in the region where the drain current is unsaturated and at negative drain voltage. >