Effect of pressure on the structure factor of liquid alkali metals

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Abstract
The structure factors S( kappa ) under a pressure P are calculated for five alkali metals near the melting curve T=Tm(P) within the interval of compressions u identical to 1- Omega (P)/ Omega (0) from 0 to 0.3. The Percus-Yevick approximation and the pseudopotential model are used which give a rather accurate description of S( kappa , T) in the metals at P=0. The calculated structure factors vary with u much more sharply than those calculated using the hard-sphere approximation and the variational method for free energy. For example, the height Sp of the S( kappa ) main peak increases by 20-25% under a compression u=0.1 and by more than 1.5 times at u=0.2. The conjecture of Ferraz and March (1980) on the existence of the 'crystallisation criterion' of the type Sp(Tm)=constant has not been confirmed by these calculations. Comparison with experiment is hindered by the spread in data available on S( kappa , u). However, the results of the virial equation of state appear to imply that the calculated S( kappa , u) are precise enough for u<or approximately=0.1 and become less accurate under higher compressions.