Structure and electronic states of expanded and compressed liquid alkali metals by ab initio molecular-dynamics simulation

The structural and the electronic properties of liquid alkali metals along the liquid-vapour coexistence curve and along the melting curve are investi gated by an ab initio molecular-dynamics (MD) simulation, which is based on the density functional theory in the local density approximation. The prec onditioned conjugate-gradient method is used to minimise the Kohn-Sham ener gy functional for each ionic configuration of the MD step. For the expanded liquid Rb along the liquid-vapour coexistence curve, it is shown that the calculated structural functions are in good agreement with the experiments and that the electronic states are strongly correlated with the ionic configuration and tend to localise due to the large spatial fluc tuation of ionic density with decreasing density. On the other hand, for the compressed liquid Rb along the melting curve, th e structural features obtained by the simulation agree well with the recent experimental results; that is, for the pressure less than 3GPa the liquid contracts uniformly but above 3GPa it starts to deviate from the simple uni form compression. This structural feature is related to the electronic s - d transition due to the high pressure, which is clearly seen in the calcula ted density of states.