[gmx-users] g_rdf and structure factor

[李德昌]

Dear gromacs users,
   I am using Gromacs 3.3 to simulate a coarse-grained molecule which contains atom B and L. The atom B and L are defined myself. When the simulation finished, I tried to use g_rdf to calculate the static structure factor. But it gave the error message:
   
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Program g_rdf, VERSION 3.3
Source code file: gmx_rdf.c, line: 817

Fatal error:

Error: atom type (B) not in list (18 types checked)!

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   I've read the source code of g_rdf, found that the variable CM_t[] only contains 18 atom types. I think it is the root of the above error, right? I want to add my user-defined atoms into the code, but I found that the program uses the Cromer Mann formula to reproduce the experimental scattering factors, can anyone tell me how I choose the nine Cromer Mann formula coefficients of my atoms?
   Why it don't use the following formula to calculate the structure factor?
   S(k)=1+4*pi*density*integral{r^2*sin(kr)/k/r*g(r)*dr}

   Thank you for your answers.  ^_^