[CP2K-user] [CP2K:17620] Re: Large discrepancy in xTB results from CP2K vs DFTB+
Xavier Bidault
jazzquark at gmail.com
Wed Sep 7 00:16:08 UTC 2022
Thank you. Could you remind me how to update CP2K 2022.1 to include this
bug fix?
On Tue, Sep 6, 2022 at 10:36 AM Jürg Hutter <hutter at chem.uzh.ch> wrote:
> Hi
>
> the updates are now on Github (Trunk version).
> This should at least fix the strange behavior for changes of EPS_DEFAULT.
>
> regards
>
> JH
>
> ________________________________________
> From: cp2k at googlegroups.com <cp2k at googlegroups.com> on behalf of Jürg
> Hutter <hutter at chem.uzh.ch>
> Sent: Tuesday, September 6, 2022 11:37 AM
> To: cp2k at googlegroups.com
> Subject: Re: [CP2K:17614] Re: Large discrepancy in xTB results from CP2K
> vs DFTB+
>
> Hi
>
> I think I found the problem. This is in fact a bug in CP2K and is related
> to the damping of
> the "short range" part of the Coulomb term. As mentioned before this short
> range part
> is not short range at all, even diverging in periodic systems. We use a
> damping function
> for this term and the radius is taken from the range of the basis function
> on each atom.
> The bug is now, that this range is not a constant but depends on
> EPS_DEFAULT.
> I will work on a solution, but at least the default settings will cause
> considerable changes
> in the energies of periodic systems.
>
> regards
>
> JH
>
> ________________________________________
> From: cp2k at googlegroups.com <cp2k at googlegroups.com> on behalf of Magnus
> Rahm <magnus at compulartech.com>
> Sent: Monday, September 5, 2022 3:19 PM
> To: cp2k
> Subject: Re: [CP2K:17609] Re: Large discrepancy in xTB results from CP2K
> vs DFTB+
>
> Hi,
>
> Thank you for valuable input! Here's a breakdown of energies for a
> periodic LiO2 system (where CP2K and DFTB+ disagree).
> CP2K:
>
> Core Hamiltonian energy:
> -609.45757320827579
> Repulsive potential energy:
> 2.86335541921533
> Electronic energy:
> -65.73940900376786
> DFTB3 3rd order energy:
> 9.00274299587460
> Dispersion energy:
> -2.00065978643714
> Correction for halogen bonding:
> 0.00000000000000
>
> Total energy:
> -665.33154358339084
>
> outer SCF iter = 1 RMS gradient = 0.49E-06 energy =
> -665.3315435834
> outer SCF loop converged in 1 iterations or 10 steps
>
> And the same system with DFTB+ (I don't know this is the best breakdown I
> can get from DFTB+? This info is from detailed.out.):
>
> Fermi level: -0.1574062769 H -4.2832 eV
> Band energy: -254.9890864567 H -6938.6061 eV
> TS: 0.0000000000 H 0.0000 eV
> Band free energy (E-TS): -254.9890864567 H -6938.6061 eV
> Extrapolated E(0K): -254.9890864567 H -6938.6061 eV
> Input / Output electrons (q): 864.0000000000 864.0000000000
>
> Energy H0: -610.3586854777 H -16608.7049 eV
> Energy SCC: 13.1915555608 H 358.9605 eV
> Total Electronic energy: -597.1671299169 H -16249.7444 eV
> Repulsive energy: 0.0000000000 H 0.0000 eV
> Total energy: -597.1671299169 H -16249.7444 eV
> Extrapolated to 0: -597.1671299169 H -16249.7444 eV
> Total Mermin free energy: -597.1671299169 H -16249.7444 eV
> Force related energy: -597.1671299169 H -16249.7444 eV
>
>
> ----------------------------------------------------------------------------------------------------------------
> For reference, here are the equivalent breakdowns for the LiF molecule,
> where the total energies do match quite well.
> CP2K:
>
> Core Hamiltonian energy:
> -5.57594122418510
> Repulsive potential energy:
> 0.00036401843654
> Electronic energy:
> 0.08477836575096
> DFTB3 3rd order energy:
> -0.00385103760005
> Dispersion energy:
> -0.00008325087778
> Correction for halogen bonding:
> 0.00000000000000
>
> Total energy:
> -5.49473312847544
>
> outer SCF iter = 1 RMS gradient = 0.12E-06 energy =
> -5.4947331285
> outer SCF loop converged in 1 iterations or 25 steps
>
> DFTB+
> Fermi level: -0.3434874008 H -9.3468 eV
> Band energy: -3.7493389034 H -102.0247 eV
> TS: 0.0000000000 H 0.0000 eV
> Band free energy (E-TS): -3.7493389034 H -102.0247 eV
> Extrapolated E(0K): -3.7493389034 H -102.0247 eV
> Input / Output electrons (q): 8.0000000444 8.0000000000
>
> Energy H0: -5.5743451431 H -151.6856 eV
> Energy SCC: 0.0807122067 H 2.1963 eV
> Total Electronic energy: -5.4936329365 H -149.4894 eV
> Repulsive energy: 0.0000000000 H 0.0000 eV
> Total energy: -5.4936329365 H -149.4894 eV
> Extrapolated to 0: -5.4936329365 H -149.4894 eV
> Total Mermin free energy: -5.4936329365 H -149.4894 eV
> Force related energy: -5.4936329365 H -149.4894 eV
>
>
> ----------------------------------------------------------------------------------------------------------------
>
> > I recently run variable-cell optimization of various molecular crystals
> and I found xTB at CP2K ultra sensitive to EPS_DEFAULT. Tested from 1e-5 to
> 1e-24 (with EPS_SCF 1e-8), and no convergence happened.
>
> Thank you for sharing this info! I tried a series of calculations with
> LiO2 using varying values of EPS_DEFAULT (using default EPS_SCF) and found
> the same effect; no convergence with EPS_DEFAULT (or perhaps unreasonably
> slow convergence). I attach a figure showing these results, including the
> energy broken down into the different parts as specified in the CP2K
> output. Note the energy scale, the changes with EPS_DEFAULT are really
> quite substantial. In the LiF (non-PBC) case, the corresponding curves look
> completely flat on the same scale. I don't know what to make of this
> result, but perhaps someone else does?
>
> Magnus
>
> [X]
> On Monday, September 5, 2022 at 12:18:26 PM UTC+2 jazz... at gmail.com wrote:
> I recently run variable-cell optimization of various molecular crystals
> and I found xTB at CP2K ultra sensitive to EPS_DEFAULT. Tested from 1e-5 to
> 1e-24 (with EPS_SCF 1e-8), and no convergence happened. I just ended up
> with EPS_DEFAULT 1e-10 as a "gut" choice. Also, the behavior of xTB at CP2K
> is doutfull with MD even at ambiant conditions, where the converged volume
> is barely larget than at 0K. Depending on EPS_DEFAULT, it can even be
> smaller at ambient T. Weird. The behavior of DFTB2 at CP2K is far better.
>
> I found that DFTB+ has other issues. xTB at DFTB+ has no convergence issue,
> but the recommended variable-cell optimization algorithm has flaws. The
> unit cell and a supercell does NOT always end up with related lattice
> parameters. The main issue is that some 90° angles are not preserved with
> DFTB+ whereas CP2K does (with no symmetry enforced, obviously). Some
> inconsistencies appears in DFTB+ with a lattice dimensions < 10 angstroms
> in the unit cell versus > 10 angstroms in the supercell. A proper tight
> mesh of k-points does not improve. So I'm afraid that xTB at DFTB+ (or
> DFTB+, actually) cannot be a relevant choice for crystal structure
> predictions, for instance.
>
> xTB may be unreliable with CP2K and DFTB+, but for the different reasons
> above. You can check these weird behaviors with your own crystals of
> interest.
>
> Xavier
>
>
>
> Le lun. 5 sept. 2022, 3:59 AM, Jürg Hutter <hut... at chem.uzh.ch> a écrit :
> Hi
>
> thank you for testing. Could you send a break down of the energies for the
> LiF molecule for
> the two codes? That might help to recognize the source of the difference.
>
> regards
>
> JH
>
> ________________________________________
> From: cp... at googlegroups.com <cp... at googlegroups.com> on behalf of Magnus
> Rahm <mag... at compulartech.com>
> Sent: Monday, September 5, 2022 8:40 AM
> To: cp2k
> Subject: [CP2K:17599] Re: Large discrepancy in xTB results from CP2K vs
> DFTB+
>
> For the record, the problem is the same in CP2K version 2022.1.
>
> On Thursday, September 1, 2022 at 12:48:35 PM UTC+2 Magnus Rahm wrote:
> Dear all,
>
> I want to use CP2K (version 8.2, trying to get a more recent version
> compiled) together with xTB for a crystal containing Li and O. I get
> strange results already for a simple LiO2 crystal:
>
> * There is a very large discrepancy compared to DFTB+ (version 22.1).
> * Mulliken charges tend to be large, meaning that CHECK_ATOMIC_CHARGES
> stops the SCF. If I turn it off, the system tends to converge
> systematically to values just outside the "chemical range". Mulliken
> charges obtained by DFTB+ are significantly smaller (and within "chemical
> range").
> * The energy-volume curve looks strange and very different from DFTB+.
>
> I have tried converging with respect to system size and the EWALD / ALPHA
> and GMAX parameters, but they have only a marginal impact. I have tried
> similar calculations for a number of periodic systems. Sometimes I get
> agreement, sometimes not. I also tried calculations for CO and NO molecules
> which agree perfectly between CP2K and DFTB+, whereas an artificial LiF
> molecule does not.
>
> A perhaps related issue was reported in
> https://groups.google.com/g/cp2k/c/oFwgGcQuySs but the solutions
> suggested there did not solve my problem.
>
> I attach input scripts for CP2K and DFTB+, as well as a figure showing the
> E-V curve for LiO2 obtained with CP2K and DFTB+. I'm new to CP2K, DFTB+ and
> xTB so I suspect I have made some simple mistake, and any advice is
> appreciated.
>
> Kind regards,
> Magnus Rahm
>
>
>
>
>
>
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