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

[Alaska Subedi]

On Thu, Sep 22, 2016 at 6:03 PM, Paolo Giannozzi <p.giannozzi at gmail.com> wrote:
> Once the error is detected, the code stops immediately and prints nothing
> useful. Where do you see that there are no cell parameters? And when: during
> a variable-cell calculation, or also (or only) in a fixed-cell one? If I
> remember correctly, cell parameters are reprinted on putput at each step in
> the former case, never in the latter.

In a vc-relax calculation, the code prints atomic_positions but not
cell_parameters after this error. Generally, vc-relax prints both
cell_parameters and atomic_positions. But this does not happen when
the code stops with this error. It would be nice if it also printed
cell_parameters before exiting.

Thanks,
Alaska


>
> Unfortunately the code performing the various MD and structural
> optimizations is rather obscure and it is not straightforward to figure out
> how to modify it.
>
> Paolo
>
> On Thu, Sep 22, 2016 at 2:56 PM, Alaska Subedi <asubedi at gmail.com> wrote:
>>
>> Dear Paolo,
>>
>> Sorry to resurrect this after a long time.
>>
>> This problem is innocuous but annoying nonetheless. I am using QE to
>> relax structures generated by USPEX. For around five percent of the
>> structures, I get this error. When this error happens, pw.x exits by
>> only printing atomic positions but not the cell parameters. This gives
>> problems to USPEX.
>>
>> I tried to find which call to output_tau is responsible for this, to
>> no avail. I'd greatly appreciate if someone can point me to a
>> modification that will make the code output both the cell_parameters
>> and atomic_positions during exit after this error.
>>
>> Thanks,
>> Alaska
>>
>>
>>
>> On Mon, Sep 22, 2014 at 9:52 PM, Paolo Giannozzi
>> <paolo.giannozzi at uniud.it> 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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>> >
>> > --
>> > Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
>> > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
>> > Phone +39-0432-558216, fax +39-0432-558222
>> >
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>
>
>
>
> --
> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
>
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