AMBER Archive (2007)

Subject: Re: AMBER: SCF convergence issues

From: Steven Winfield (saw44_at_cam.ac.uk)
Date: Fri Mar 02 2007 - 07:43:58 CST

Dear Ross

Thanks for your previous help.

>> I built the system from a few TIP3PBOXs, manually adjusted the box
>> dimensions to give the correct density at 300K, performed a
>> few thousand
>> minimisation steps (about half steepest descent), then
>> performed MD from
>> 0K -> 300K over 100ps, followed by another 100ps at 300K, both NVT.
>
> Was this with QM/MM MD? If so then is definately a problem with
> incompatibility ofr dumpfrc and QMMM.

No, this was done classically. I've bitten the bullet and am now
equilibrating a larger (45A cube) box of water, again classically:

10000 steps minimisation (2000 steepest descent)
200ps NVT 0K -> 300K
1ns NPT 300K

Should I do some minimisation after this with QM/MM turned on before I
do QM/MM MD?

> The safer way would just be to put a write(20,*) f(1:3*natom) at the end of
> the force routine followed by a call to mexit but this obviously involved
> adding a couple of lines to force.f. I don't know if you would be okay to do
> this or not.

Thanks for the suggestion.

Regards,

Steve.
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