[Pw_forum] Converged SCF total energies different in 6.0/6.1/6.2

[WF]

Thanks very much for this important information.

Best regards,
Feng

>See this note in file Doc/release-notes:
>
>  * Some constants in the definition of PBE functionals were truncated to
>    6 significant digits. While not a bug, this could lead to tiny
differences
>    with respect to previous results and other XC implementations (r13592)
>
>More explicitly: some constants that previously were truncated to 6 digits,
are now defined with full precision. This removes minor numerical
discrepancies with the results obtained using libxc.
>
>Paolo

>On Thu, Dec 21, 2017 at 3:11 AM, WF <kalamaillist at gmail.com> wrote:

>> Dear all,
>>
>> In tests a normal DFT calculations with Si, I noticed that QE 6.0 and 
>> 6.1 gives exactly same total energy with 6.0 and 6.1 (-15.75190880 
>> Ry), but with QE 6.2.1, the total energy is -15.75191309Ry. I tested 
>> this on two different machines with different compilers, the results 
>> are the same across all of them (at least to last digit). I did some 
>> tests on larger systems also and found even larger difference. This 
>> 1e-5 Ry order of difference is not negligible. Is there anything 
>> introduced in 6.2 leads to this difference? Thanks very much.
>>
>>
>>
>> Best regards,
>>
>> Feng
>>
>>
>>
>>
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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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Dr. Feng Wu
Postdoctoral researcher
Department of Chemistry and Biochemistry
University of California, Santa Cruz
Phone: 831-459-2874