simin.... at gmail.com
Tue Apr 24 11:16:54 UTC 2018
I would like to thank you very much for your Helpful comments again.
Have a nice day
On Tuesday, April 24, 2018 at 12:42:37 PM UTC+2, Matt W wrote:
> Personal opinion is that converging total energy is not very important in
> this case - it is normally just a rigid shift based on inaccuracy of the
> core part of the wavefunctions. I am still (again personally) not really a
> big fan of the smoothing, I'd rather have a slightly bigger cutoff but a
> not messed with functional.
> I would look at forces on atoms and see how they converge and see how
> errors in forces propagate to energy conservation.
> On Tuesday, April 24, 2018 at 10:24:34 AM UTC+1, simin pahlavi wrote:
>> Hello Matteu
>> Thank you very much fir your helpful comment.
>> As I am supposed to use this DFT calculations for every step of an ab
>> initio molecular dynamics, I wonder if I should
>> go for the heavy smoothing and get reasonable forces or I should be worry
>> about convergence and cutoff dependence of minimization?
>> I appreciate any reply in advance
>> On Monday, April 23, 2018 at 10:41:00 PM UTC+2, Matt W wrote:
>>> Sorry, I posted too quickly without really looking at your setup.
>>> The big problem for you is the XC_GRID settings.
>>> XC_SMOOTH_RHO NN50
>>> XC_DERIV NN50_SMOOTH
>>> &END XC_GRID
>>> You really do not want to be using heavy smoothing, especially for this
>>> purpose. These settings (see original paper) help get reasonable forces
>>> with a rather low cutoff, but as you increase the cutoff lead to you
>>> continuously redefining the XC functional you use (you are smoothing over
>>> different areas of real space), so they do not converge.
>>> Try changing to the defaults
>>> XC_SMOOTH_RHO NONE
>>> XC_DERIV PW
>>> &END XC_GRID
>>> you should see at least a significant improvement.
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