[CP2K:6254] Energy conservation in periodic QM/MM
Dorothea Golze
dorothe... at googlemail.com
Wed Mar 18 09:22:38 UTC 2015
Hi,
if you have a fully periodic setup where the QM and MM boxes are equal, you
do not need the decoupling/recoupling stuff, i.e. switch off explicitly the
MULTIPOLE section like that
&MULTIPOLE OFF
&END
Also set in the QMMM section
&WALLS
TYPE NONE
&END WALLS
That should address your first question...
Cheers,
Dorothea
2015-03-18 8:46 GMT+01:00 Jonggu Jeon <jeonj... at gmail.com>:
> Dear CP2K users,
>
> I'd like to ask some questions on the capabilities of the QM/MM part of
> CP2K (I'm using version 2.5.1, svn:13632).
>
> I've been attempting a QM/MM MD simulation with CP2K. My system consists
> of one NMA molecule (TZV2P/BLYP DFT) and 48 methanol molecules (OPLS MM
> force field).
> The relevant parts of my input file are attached at the end of the
> message. Basically, I'm following all the advices from this group for a
> fully periodic QM/MM setup and set the cell sizes for the QM (in QMMM/CELL)
> and MM (in SUBSYS/CELL) parts equal.
>
> The following is the summary of my findings.
>
> 1. With FORCE_EVAL/QMMM/CENTER EVERY_STEP, the total energy is not
> conserved, as pointed out by Dr. Laino in this group before.
> 2. With FORCE_EVAL/QMMM/CENTER SETUP_ONLY, the total energy is very well
> conserved within 0.1 kcal/mol for a few ps until the QM molecule eventually
> crosses the cell boundary. At this point system energy shoots up by
> several kcal/mol and the output begins to produce the following messages:
>
> *** 16:11:03 WARNING in qmmm_util:apply_qmmm_walls_reflective :: One or
> ***
> *** few QM atoms are within the SKIN of the quantum box. Check your run
> ***
> *** and you may possibly consider: the activation of the QMMM WALLS
> ***
> *** around the QM box, switching ON the centering of the QM box or
> ***
> *** increase the size of the QM cell. CP2K CONTINUE but results could be
> ***
> *** meaningless. qmmm_util.F line 206
> ***
>
> My questions are as follows:
>
> 1. Is it possible to achieve the energy conservation in a fully periodic
> DFT/MM MD without worrying about the QM molecule crossing the cell
> boundary? I believe this is possible in full DFT MD but my experience on
> CP2K QM/MM so far indicates otherwise. I'd appreciate if someone can
> provide an answer and keywords to achieve it.
>
> 2. The QMMM/CENTER option affects energy conservation a lot. When CENTER
> EVERY_STEP is used, would it improve energy conservation if I use finer
> grids by increasing DFT/MGRID/CUTOFF value?
>
> The skeletal form of my input file is attached below.
> Thank you.
>
> Jonggu Jeon
>
>
>
> &MOTION
> &MD
> ENSEMBLE NVE
> STEPS 40000
> TIMESTEP 0.5
> STEP_START_VAL 0
> TIME_START_VAL 0
> &END MD
> &END MOTION
> &FORCE_EVAL
> METHOD QMMM
> &DFT
> BASIS_SET_FILE_NAME /opt/cp2k/2.5.1/tests/QS/GTH_BASIS_SETS
> POTENTIAL_FILE_NAME /opt/cp2k/2.5.1/tests/QS/POTENTIAL
> WFN_RESTART_FILE_NAME wfn.rst
> CHARGE 0
> &SCF
> MAX_SCF 30
> EPS_SCF 9.9999999999999995E-07
> SCF_GUESS RESTART
> &OT T
> MINIMIZER DIIS
> PRECONDITIONER FULL_ALL
> ENERGY_GAP 1.0000000000000000E-03
> &END OT
> &OUTER_SCF T
> EPS_SCF 9.9999999999999995E-07
> MAX_SCF 1
> &END OUTER_SCF
> &END SCF
> &QS
> EPS_DEFAULT 1.0000000000000000E-10
> MAP_CONSISTENT T
> EXTRAPOLATION ASPC
> EXTRAPOLATION_ORDER 3
> METHOD GPW
> &END QS
> &MGRID
> CUTOFF 2.8000000000000000E+02
> COMMENSURATE T
> &END MGRID
> &XC
> &XC_GRID
> XC_SMOOTH_RHO NN50
> XC_DERIV SPLINE2_SMOOTH
> &END XC_GRID
> &XC_FUNCTIONAL NO_SHORTCUT
> &BECKE88 T
> &END BECKE88
> &LYP T
> &END LYP
> &END XC_FUNCTIONAL
> &VDW_POTENTIAL
> POTENTIAL_TYPE PAIR_POTENTIAL
> &PAIR_POTENTIAL
> TYPE DFTD3
> PARAMETER_FILE_NAME /opt/cp2k/2.5.1/tests/QS/dftd3.dat
> REFERENCE_FUNCTIONAL BLYP
> CALCULATE_C9_TERM F
> REFERENCE_C9_TERM F
> LONG_RANGE_CORRECTION F
> &END PAIR_POTENTIAL
> &END VDW_POTENTIAL
> &END XC
> &END DFT
> &MM
> &FORCEFIELD
> PARMTYPE AMBER
> PARM_FILE_NAME ndmd48.ao.prmtop
> &SPLINE
> EMAX_SPLINE 1.0000000000000000E+00
> &END SPLINE
> &END FORCEFIELD
> &POISSON
> &EWALD
> EWALD_TYPE SPME
> ALPHA 3.4999999999999998E-01
> GMAX 18
> &END EWALD
> &END POISSON
> &END MM
> &QMMM
> E_COUPL GAUSS
> USE_GEEP_LIB 7
> NOCOMPATIBILITY T
> CENTER SETUP_ONLY
> INITIAL_TRANSLATION_VECTOR -1.0888775605157457E+01
> -2.9066675351256084E+00 7.3922596274008097E+00
> &CELL
> ABC 1.5084868700000001E+01 1.5084868700000001E+01
> 1.5084868700000001E+01
> PERIODIC XYZ
> &END CELL
> &PERIODIC
> GMAX 5.0000000000000000E-01
> &MULTIPOLE
> RCUT 1.2000000000000000E+01
> EWALD_PRECISION 4.9999999999999998E-07
> ANALYTICAL_GTERM T
> NGRIDS 50 50 50
> &END MULTIPOLE
> &END PERIODIC
> &END QMMM
> &SUBSYS
> &CELL
> A 1.5084868700000001E+01 0.0000000000000000E+00
> 0.0000000000000000E+00
> B 0.0000000000000000E+00 1.5084868700000001E+01
> 0.0000000000000000E+00
> C 0.0000000000000000E+00 0.0000000000000000E+00
> 1.5084868700000001E+01
> MULTIPLE_UNIT_CELL 1 1 1
> &END CELL
> &TOPOLOGY
> NUMBER_OF_ATOMS 156
> CONN_FILE_NAME ndmd48.ao.prmtop
> CONN_FILE_FORMAT AMBER
> MULTIPLE_UNIT_CELL 1 1 1
> &END TOPOLOGY
> &END SUBSYS
> &END FORCE_EVAL
>
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