[Pw_forum] Error in routine bfgs (1): dE0s is positive which should never happen

[Lorenzo Paulatto]

In this specific case, as dispersion correction is a relatively new 
addition to the code, it /may/ also be caused by some minor bug causing 
energy and forces to not be perfectly consistent. I can tell from 
experience that even a difference as small as 10^-5 Ry can cause BFGS to 
fail when close to the minimum.

It would take some very careful finite difference calculation to, 
possibly performed by someone who knows the dispersion correction code, 
to be 100% sure. However I would say that for most purposes you can 
proceed with no worries, and eventually use damped dynamics for the last 
part of the geometry optimization.

regards


On 09/22/2014 09:52 PM, Paolo Giannozzi wrote:
> This kind of errors invariably happens when you are very close
> to the minimum and you have some numerical noise on forces. It
> is useless in my opinion to insist: your system is sufficiently
> relaxed
>
> Paolo
>
> On Mon, 2014-09-22 at 13:29 +0530, amitharani wrote:
>> Hi
>> I am getting an error { Error in routine bfgs (1): dE0s is positive
>> which should never happen }. The output file is attached for your kind
>> perusal.This is the 2nd time I am getting the same error consecutively.
>> I followed what Nick had suggested on the pwforum to take the relaxed
>> co-ordinates, make a new input file and resubmit, but it didn't
>> work.Thanks.
>>
>>
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-- 
Lorenzo Paulatto - Paris 18

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