STRUCTURE FACTOR OF X4 TETRAHEDRAL MOLECULAR LIQUIDS - COMPETITION BETWEEN INTRAMOLECULAR AND INTERMOLECULAR ATOMIC SPACINGS

Structure factor Sm (Q) of liquids of simple tetrahedral molecules X4 has been calculated as a function of ζ, where ζ is a ratio of the intermolecular atomic spacing L to the intramolecular atomic spacing l, i.e., ζ = L/l, under constraints of a fixed preferred orientation between the nearest neighbors and a fixed packing fraction of uncorrelated molecules. It turned out that the Sm, (Q) depends strongly on the ratio ζ. An important feature of the calculated S m (Q)'s is an appearance of a new peak at low Q region and its rapid growth with increasing ζ. The characteristic features of the experimental Sm (Q)'s of liquids P4 and VCl4 can be reasonably reproduced by the present simple calculation with ζ = 1.64 for liquid P4 and 1.14 for liquid VCl4. These values of ζ are simply interpreted by the molecular size and intramolecular atomic spacing of each molecule. © 1990 American Institute of Physics.