[gmx-users] rvdw>rlist for nve simulation

[David]

On Tue, 2004-05-04 at 06:56, Linda wrote:
> Hi, all, 
> 
> 	I found gmx3.2.1 has fixed "rlist > rcoulomb" problem when executing grompp, while it still gives error message "With vdwtype = Cut-off,rvdw must be >= rlist" when setting "rlist > rvdw". I want to keep energy conserve when running NVE ensemble MD, so although someones have pointted out one must fix it by changging code, while I do not find how to fix it in mailing list archive. Can somebody help?? 
> 

did you change rvdw_switch as well? that should be at least 1 Å smaller
than rvdw for shifting.

> it is OK by just simply commenting out following code in src/kernel/readir.c?
> 
>   if ((ir->vdwtype == evdwSWITCH) || (ir->vdwtype == evdwSHIFT)) {
>     sprintf(err_buf,"With vdwtype = %s rvdw_switch must be < rvdw",
>             evdw_names[ir->vdwtype]);
>     CHECK(ir->rvdw_switch >= ir->rvdw);
>     if (ir->rvdw_switch > ir->rvdw-0.0999) {
>       sprintf(warn_buf,"rvdw should be 0.1 to 0.3 nm larger than rvdw_switch to account for diffusion and the size of charge groups");
>       warning(NULL);
>     }
>   } else {
>     sprintf(err_buf,"With vdwtype = %s,rvdw must be >= rlist",evdw_names[ir->vdwtype]);
>     CHECK(ir->rlist > ir->rvdw);
>   }
> 
>  	Please correct me if I am wrong. Thx!

Probably, if you run mdrun -debug it will print out the tables used for
the LJ potential. These you can check with xmgrace

-- 
David.
________________________________________________________________________
David van der Spoel, PhD, Assoc. Prof., Molecular Biophysics group,
Dept. of Cell and Molecular Biology, Uppsala University.
Husargatan 3, Box 596,  	75124 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://xray.bmc.uu.se/~spoel
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++