Size-extensive calculations of static structure factors from the coupled cluster singles and doubles model

The x-ray incoherent scattering factor S(q), which is also called the static structure factor, is very sensitive to electron correlation. In this study a method for calculating S(q) based on coupled cluster singles and doubles (CCSD) approach is developed and the computed S(q) of H2O, CH3OH, CH3CN, C6H6, and C6H12 are compared with experimental results. It is shown that the CCSD method improves theoretical S(q) of large molecules significantly compared with those by configuration interaction singles and doubles (CISD) previously employed.