printf("\nPlease select group for SANS spectra calculation:\n");
get_index(&(top->atoms), ftp2fn_null(efNDX, NFILE, fnm), 1, &isize, &index, grpname);
printf("\nPlease select group for SANS spectra calculation:\n");
get_index(&(top->atoms), ftp2fn_null(efNDX, NFILE, fnm), 1, &isize, &index, grpname);