Wallerndash;Hartree calculations of molecular incoherent scattering factorsS(thinsp;mgr;) for CH4, NH3, and H2O are reported to provide an unambiguous comparison with recent calculations ofS(thinsp;mgr;) for these molecules made by integration of impulse approximation Compton profiles. It is found that the latter approach leads to both qualitative and quantitative errors at small momentum transfer mgr;. Moreover, it is pointed out that Wallerndash;Hartree calculations ofS(thinsp;mgr;) require very little additional effort when one is calculating elastic cross sections. An illustrative calculation for diborane is used to suggest that even selfhyphen;consistent field calculations of the Wallerndash;HartreeS(thinsp;mgr;) can be useful in the analysis of experimental data provided that some caution is used and that the calculations are approximately corrected for electron correlation effects.
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