X-Ray Determination of the Static Structure Factor of Liquid Na and K

Highly accurate x-ray diffraction measurements are presented for the static structure factor $a(q)$ for liquid Na (at 100 and 200 ^∘{}C) and liquid K (at 65 and 135 ^∘{}C). A detailed error analysis is presented showing that the over-all root-mean-square error in $a(q)$ never exceeds 2.5% for any value of the momentum transfer q and the relative root-mean-square error in $a(q)$ between different temperatures is always less than 1.5%. We discuss and demonstrate the reliability of the tabulated values for the atomic form factor and the Compton-scattering correction. A brief discussion is included of the relative merits of x-ray vs neutron diffraction for obtaining the static structure factor.