[CP2K-user] [CP2K:13176] bulk cell opt questions

Thomas Kühne tku... at gmail.com
Mon Apr 27 21:42:10 UTC 2020

Dear Jing, 

honestly I don’t fully understand what you are testing and what is the rational behind it. 
However, first of all you can’t compare the absolute energies (there are not even 
expected to be close), since you are comparing a pseudopotential calculation with an 
all electron reference. Also, I suspect that your reference is a gas phase calculation, 
which can neither compared to your periodic test no. 1 (because of pbc) and also 
not to test no. 2, which is not a proper isolated supercell due to too small cell dimensions 
along the x-direction.


> Am 27.04.2020 um 11:25 schrieb Jing Liu <liujin... at gmail.com>:
> Dear CP2K users
> Recently I'm trying to run the cell optimization for a organic material (Tetraazapyrene). My goal is to optmize the cell parameters of this bulk system. 
> However during the test run there are few things that I could not explain, it's very likely that I missed something so if anyone could point them out would be very appreciated.
> The test cases are:
> Test_1: using the cif file, set pbc x y z both in &CELL and &POISSON, initial cell parameters are taken from cif file, no super cell
> Test_2: using the same cif file as Test_1, set pbc x y z both in &CELL and &POISSON, initial cell parameters are taken from the same cif file as Test_1, 2*2*2 super cell, set charge constraint to 0
> Reference: single TAPP molecule, geo_opt with KOALA at cc2 level
> The problems are:
> In Test_1: total energy of the converged run greatly dffered with respect to the reference run. They of course should not be identical but also should be close. Total energy of this run is: -340.2863 H. 
> In Test_2: Total energy difference increased, total charge is also wrong despite the constraint was applied. Total energy of this is: -2722.1877 H, total charge of this run is: 0 (for Mulliken) and 1.2 (for Hirshfeld)
> In Reference: Total energy is: -1061.3367 H.
> All the inp and out files are attached.
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> <hth.cif><hth_supercell.inp><hth.inp><hth_bulk_cell_opt_supercell_reduced.out><hth_bulk_cell_opt_reduced.out><koala_cc2_geo_opt_last_iter_reduced.out>

Thomas D. Kühne
Dynamics of Condensed Matter
Chair of Theoretical Chemistry
University of Paderborn
Warburger Str. 100
D-33098 Paderborn
tdku... at mail.upb.de

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