[CP2K-user] [CP2K:19661] periodic HF with TC-LRC in a non-orthogonal cell

[Augustin Bussy]

Dear Martin,

Internally, CP2K calculates the shortest distance between lattice planes, and check whether this distance is at least twice the TC cutoff radius. In non-orthorhombic cells such as yours, this distance might not necessarily be equal to a cell vector.

Best,
Augustin
________________________________
From: cp2k at googlegroups.com <cp2k at googlegroups.com> on behalf of Martin Konôpka <konopka2010 at gmail.com>
Sent: Thursday, December 14, 2023 9:30 PM
To: cp2k <cp2k at googlegroups.com>
Subject: [CP2K:19662] periodic HF with TC-LRC in a non-orthogonal cell

Dear CP2K experts,

I started a single-point energy calculation with the PBE0 functional using the TC-LRC and ADMM techniques. I have set
     CUTOFF_RADIUS  5.8
in both  PBE_HOLE_T_C_LR  and  INTERACTION_POTENTIAL sections. My cell is specified by

    &CELL
      A     11.8510781995796848      0.0000000000000000      0.0000000000000000
      B      3.0393557951773005     15.1183691669733679      0.0000000000000000
      C     -9.9987074440890415      4.4935205367592285     12.8517421729587179
      PERIODIC  XYZ
    &END CELL
which is understood in angstroms. The above cutoff is also in angstroms. So, the shortest cell size is about 11.85 angstroms. Despite of that, cp2k prints the warning message:

 *** WARNING in hfx_types.F:1968 :: Periodic Hartree Fock calculation      ***
 *** requested with use of a truncated or shortrange potential. The cutoff ***
 *** radius is larger than half the minimal cell dimension. This may lead  ***
 *** to unphysical total energies. Reduce the cutoff radius in order to    ***
 *** avoid possible problems.                                              ***

Otherwise the calculation seems to run smoothly and Etot is a similar quantity to the one from the PBE calculation at the same geometry. The code version is 9.1. Should I really worry about the warning? Are the TC-LRC and ADMM techniques fully implemented for non-orthogonal cells?

Thank you very much for your advices.

Best regards
Martin Konôpka.

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