[CP2K-user] Different values of "Total energy"  and " ENERGY| Total FORCE_EVAL" for a QS-DFT cal with no smearing.

Unmesh Mondal unmesh... at students.iiserpune.ac.in
Tue Apr 7 09:19:43 UTC 2020

Dear Users,

As a follow up to my previous question, which subroutine of the code deals 
with the calculation of  final free energy (" ENERGY| Total FORCE_EVAL") 
from the DFT energy ("Total energy") in QS-DFT? 

The difference in the above mentioned quantities raises a doubt about the 
forces on the atoms used in dynamics. Can someone please let me know which 
energy quantity (amongst the two) is used to calculate the forces on atoms 
(I have not used any smearing in the calculation)?  

Please correct me if I have misunderstood any part.  

Unmesh Mondal

On Thursday, March 19, 2020 at 2:32:40 AM UTC+5:30, Unmesh Mondal wrote:
>  Dear Cp2k users,
> For a DFT calculation with no smearing, we expect the "Total energy"  and 
> " ENERGY| Total FORCE_EVAL" to be same, as mentioned in 
> https://www.cp2k.org/howto:static_calculation
> But, for a PIGLET MD simulation where cp2k is the client and i-pi(
> http://ipi-code.org/) is the host, I find the above two quantities to be 
> different for a particular scf step. Attached is the output(pimd_gle_4.out: 
> line number: 8442) where I find this anomaly.
> (The job script fires multiple instances of the cp2k executable with each 
> running on separate node.)
> What can be the reason for such an anomaly?
> How to address the anomaly?
> Also, attaching the cp2k input(in.cp2k) for the same. 
> Thanks 
> Unmesh Mondal
> IISER Pune. India
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