On 14 September 2012 13:05, Tim Gruene <[email protected]> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Dear Niu, > > as far as I can tell, all your parameters are correct and the > scattering term for f(s) you use is also correct. f(s) furthermore > matches very closely those tabulated in the Intl. Tables C Tab. 6.1.1.1. > > My reproduction of the mentioned formula with r=2.0 using MAXIMA also > shows quite a different graph. > > The graph does not make much sense: > as d_max -> 0 1/d_max -> infinity and the integrand goes to infinity,
d_min surely, i.e. minimum d-spacing? > because f(s) contains a constant positive term. Hence the integral > should oscilatingly approach infinity and not stabilise as the upper > integral limit approaches infinity. Tim, exactly so, in fact like this: http://journals.iucr.org/d/issues/2012/04/00/dz5235/dz5235.pdf See eqn 2 and Fig 11(b). Note that although rho(r) itself does indeed tend to zero as d_min -> 0 as expected, the volume integral of rho(r) (i.e. the calculated number of electrons) does not (unless d_min -> 0) ! Cheers -- Ian
