SV: [gmx-users] Error message: Cut-off length is longer than halfthe shortest box vector

[Sarah Witzke]

Which version of gromacs are you using? If you are using version 4.0 editconf will change your box dimensions to zero.

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Fra: gmx-users-bounces at gromacs.org på vegne af Mark Abraham
Sendt: ti 29-09-2009 05:48
Til: Discussion list for GROMACS users
Emne: Re: [gmx-users] Error message: Cut-off length is longer than halfthe shortest box vector



Lum Nforbi wrote:
> Hello everyone,
>       Thanks to Tsjerk, Mark Abraham, Justin and Dr. Vitaly for the very
> useful inputs to my quest for generating a .gro file from a .pdb file.
>       I am now trying to minimize the energy of the system so I can do
> an mdrun but I keep having the error message:
> the cut-off length is longer than half the shortest box vector or longer
> than the smallest box diagonal element. Increase the box size or
> decrease rlist.
>       I have changed the values of rlist, rvdw and rcoulomb,

Don't, unless you know what you're doing. Your force field is
parametrized under certain conditions, and varying these quantities by
much will remove you from conditions where the force field might be
supposed to work well. It does sound like you would benefit from doing
some general background reading about molecular mechanics force fields
and molecular dynamics simulations, and/or some more tutorial material.

> and even
> the box size several times but I still keep having this message. Please,

You can change your box size with editconf, and then you will need to
use genconf (or other) to increase the amount of solvent.

> I need help to figure out what to do to fix this problem.
> The command line I am using is:grompp -f waters.mdp -c waters_b.gro -p
> water.top -o watersinput.tpr

This command generates a (binary) run input file. It does not do
anything to the box size, which it reads from the -c file.

>       Also, is there a way to convert atom types from one format to
> another? I also have the following warnings:
>
> "Warning: atom name 1 in water.top and waters_b.gro does not match (OW - O)
> Warning: atom name 2 in water.top and waters_b.gro does not match (HW1 - H)
> Warning: atom name 3 in water.top and waters_b.gro does not match (HW2 - H)
> atom names from water.top will be used
> atom names from waters_b.gro will be ignored."
>
> I had drawn my molecule in ghemical and exported as a pdb file and so
> the atom types O and H were automatically generated.

Using the coordinate file output from pdb2gmx for subsequent operations
is the correct way to avoid these warnings. If you're not using pdb2gmx
then you need to really understand what you're doing.

Mark
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