[CP2K-user] [CP2K:14965] odd force drift convergence with respect to density cutoff

[W. Lai]

Dear Juerg,

Thanks for your comments. They make sense.  However, this does add 
complexity as we have to check the force error of the whole MD trajectory 
and then adjust the cutoff, if we want to be careful.

Thanks, Wei

On Thursday, March 18, 2021 at 12:23:24 PM UTC-4 jgh wrote:

> Hi
>
> there are two sources of errors that could be relevant for this.
>
> 1) by changing the cutoff, the relative position of the atoms within
> the real space grids change. This then leads to a change of
> energy and forces. This has been discussed before here.
> 2) By default you are using multiple grids and by changing the
> cutoff, the change in accuracy is not linear but might jump
> at certain cutoffs.
>
> best regards
>
> Juerg Hutter
> --------------------------------------------------------------
> Juerg Hutter Phone : ++41 44 635 4491 <+41%2044%20635%2044%2091>
> Institut für Chemie C FAX : ++41 44 635 6838 <+41%2044%20635%2068%2038>
> Universität Zürich E-mail: h... at chem.uzh.ch
> Winterthurerstrasse 190
> CH-8057 Zürich, Switzerland
> ---------------------------------------------------------------
>
> -----c... at googlegroups.com wrote: -----
> To: "cp2k" <c... at googlegroups.com>
> From: "W. Lai" 
> Sent by: c... at googlegroups.com
> Date: 03/18/2021 03:11PM
> Subject: [CP2K:14965] odd force drift convergence with respect to density 
> cutoff
>
> Dear CP2k users and developers,
>
> I am seeing odd behavior on how force drift(error) change as we change the 
> density cutoff value (from 400 to 1600 Ry), for a model material of SiC-6H. 
> I am using the 7.1 version and I changed the force error ("Sum of Atomic 
> Forces") to eV/A.
>
> While it is subjective to consider what is an acceptable value for the 
> force error (i.e. 0.01 or 0.001 eV/A), such oscillation really makes it a 
> difficult task to choose the appropriate cutoff.
>
> It is worth noting this is a hexagonal cell and force error is primarily 
> on the z direction. Input file is enclosed.
>
> Thanks, Wei
>
>
>
>
> &GLOBAL
> PROJECT SiC
> RUN_TYPE ENERGY_FORCE
> PRINT_LEVEL LOW
> &END GLOBAL
> &FORCE_EVAL
> STRESS_TENSOR ANALYTICAL
> METHOD QS
> &DFT
> BASIS_SET_FILE_NAME BASIS_MOLOPT
> POTENTIAL_FILE_NAME GTH_POTENTIALS
>
> &MGRID
> CUTOFF 400
> REL_CUTOFF 60
> &END MGRID
>
> &QS
> METHOD GPW
> EPS_DEFAULT 1.0E-12
> &END QS
>
> &SCF 
> SCF_GUESS ATOMIC
> MAX_SCF 100
> EPS_SCF 5.0E-8
> ADDED_MOS 60
> CHOLESKY INVERSE
> &SMEAR ON
> METHOD FERMI_DIRAC
> ELECTRONIC_TEMPERATURE [K] 300
> &END SMEAR
> &DIAGONALIZATION
> &END DIAGONALIZATION
> &MIXING
> METHOD BROYDEN_MIXING
> ALPHA 0.2
> &END 
> &PRINT
> &RESTART OFF
> &END
> &END
> &END SCF
>
> &XC
> &XC_FUNCTIONAL PBE
> &END XC_FUNCTIONAL
> &END XC
>
> &POISSON
> PERIODIC XYZ
> &END
>
> &PRINT
> &E_DENSITY_CUBE OFF
> &EACH
> MD 10
> &END EACH
> STRIDE 1 1 1 
> &END E_DENSITY_CUBE
> &END PRINT
> &END DFT
>
> &SUBSYS
> &KIND Si
> ELEMENT Si
> BASIS_SET DZVP-MOLOPT-SR-GTH
> POTENTIAL GTH-PBE
> &END KIND
> &KIND C
> ELEMENT C
> BASIS_SET DZVP-MOLOPT-SR-GTH
> POTENTIAL GTH-PBE
> &END KIND 
> &CELL
> PERIODIC XYZ
> A 9.2430000305 0.0000000000 0.0000000000
> B -4.6215010811 8.0046722182 0.0000000000
> C 0.0000000000 0.0000000000 15.1247997284
> &END CELL
>
> &COORD
> Si 0.0 0.0 0.0
> Si -1.5405004 2.6682241 0.0
> Si -3.0810008 5.3364482 0.0
> Si 3.0810001 0.0 0.0
> Si 1.5404997 2.6682241 0.0
> Si -7.1525574e-07 5.3364482 0.0
> Si 6.1620002 0.0 0.0
> Si 4.6215 2.6682241 0.0
> Si 3.0809994 5.3364482 0.0
> Si 0.0 0.0 7.5623999
> Si -1.5405004 2.6682241 7.5623999
> Si -3.0810008 5.3364482 7.5623999
> Si 3.0810001 0.0 7.5623999
> Si 1.5404997 2.6682241 7.5623999
> Si -7.1525574e-07 5.3364482 7.5623999
> Si 6.1620002 0.0 7.5623999
> Si 4.6215 2.6682241 7.5623999
> Si 3.0809994 5.3364482 7.5623999
> Si -1.1920929e-07 1.7788159 2.5208001
> Si -1.5405003 4.4470396 2.5208001
> Si -3.0810008 7.1152635 2.5208001
> Si 3.0810001 1.7788159 2.5208001
> Si 1.5405 4.4470396 2.5208001
> Si -4.7683716e-07 7.1152635 2.5208001
> Si 6.1619997 1.7788159 2.5208001
> Si 4.6215 4.4470396 2.5208001
> Si 3.0809994 7.1152635 2.5208001
> Si 1.5405 0.889408 10.0832005
> Si -4.7683716e-07 3.5576318 10.0832005
> Si -1.5405007 6.2258563 10.0832005
> Si 4.6215 0.889408 10.0832005
> Si 3.0809999 3.5576318 10.0832005
> Si 1.5404995 6.2258563 10.0832005
> Si 7.7025004 0.889408 10.0832005
> Si 6.1620002 3.5576318 10.0832005
> Si 4.621501 6.2258563 10.0832005
> Si 1.5405001 0.889408 5.0350456
> Si -2.3841858e-07 3.5576318 5.0350456
> Si -1.5405004 6.2258563 5.0350456
> Si 4.6215 0.889408 5.0350456
> Si 3.0809999 3.5576318 5.0350456
> Si 1.5404995 6.2258563 5.0350456
> Si 7.7025004 0.889408 5.0350456
> Si 6.1620002 3.5576318 5.0350456
> Si 4.621501 6.2258563 5.0350456
> Si -2.3841858e-07 1.7788158 12.5974455
> Si -1.5405004 4.4470396 12.5974455
> Si -3.0810008 7.1152635 12.5974455
> Si 3.0810003 1.7788158 12.5974455
> Si 1.5405 4.4470396 12.5974455
> Si -4.7683716e-07 7.1152635 12.5974455
> Si 6.1619997 1.7788158 12.5974455
> Si 4.6215 4.4470396 12.5974455
> Si 3.0809994 7.1152635 12.5974455
> C -1.1920929e-07 1.7788159 0.6231418
> C -1.5405003 4.4470396 0.6231418
> C -3.0810008 7.1152635 0.6231418
> C 3.0810001 1.7788159 0.6231418
> C 1.5405 4.4470396 0.6231418
> C -4.7683716e-07 7.1152635 0.6231418
> C 6.1619997 1.7788159 0.6231418
> C 4.6215 4.4470396 0.6231418
> C 3.0809994 7.1152635 0.6231418
> C 1.5405 0.889408 8.1855412
> C -4.7683716e-07 3.5576318 8.1855412
> C -1.5405007 6.2258563 8.1855412
> C 4.6215 0.889408 8.1855412
> C 3.0809999 3.5576318 8.1855412
> C 1.5404995 6.2258563 8.1855412
> C 7.7025004 0.889408 8.1855412
> C 6.1620002 3.5576318 8.1855412
> C 4.621501 6.2258563 8.1855412
> C 1.5405001 0.889408 3.1459584
> C -2.3841858e-07 3.5576318 3.1459584
> C -1.5405004 6.2258563 3.1459584
> C 4.6215 0.889408 3.1459584
> C 3.0809999 3.5576318 3.1459584
> C 1.5404995 6.2258563 3.1459584
> C 7.7025004 0.889408 3.1459584
> C 6.1620002 3.5576318 3.1459584
> C 4.621501 6.2258563 3.1459584
> C -2.3841858e-07 1.7788158 10.7083578
> C -1.5405004 4.4470396 10.7083578
> C -3.0810008 7.1152635 10.7083578
> C 3.0810003 1.7788158 10.7083578
> C 1.5405 4.4470396 10.7083578
> C -4.7683716e-07 7.1152635 10.7083578
> C 6.1619997 1.7788158 10.7083578
> C 4.6215 4.4470396 10.7083578
> C 3.0809994 7.1152635 10.7083578
> C 0.0 0.0 5.6657501
> C -1.5405004 2.6682241 5.6657501
> C -3.0810008 5.3364482 5.6657501
> C 3.0810001 0.0 5.6657501
> C 1.5404997 2.6682241 5.6657501
> C -7.1525574e-07 5.3364482 5.6657501
> C 6.1620002 0.0 5.6657501
> C 4.6215 2.6682241 5.6657501
> C 3.0809994 5.3364482 5.6657501
> C 0.0 0.0 13.2281494
> C -1.5405004 2.6682241 13.2281494
> C -3.0810008 5.3364482 13.2281494
> C 3.0810001 0.0 13.2281494
> C 1.5404997 2.6682241 13.2281494
> C -7.1525574e-07 5.3364482 13.2281494
> C 6.1620002 0.0 13.2281494
> C 4.6215 2.6682241 13.2281494
> C 3.0809994 5.3364482 13.2281494
> &END COORD
> &END SUBSYS
>
> &PRINT
> &FORCES ON
> &END FORCES
> &TOTAL_NUMBERS ON
> &END TOTAL_NUMBERS
> &END PRINT
>
> &END FORCE_EVAL
>
>
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