[CP2K:6254] Energy conservation in periodic QM/MM

[Matt W]

Hi,

there is also the CENTER_GRID that has been introduced quite recently. I 
don't know how much it has been tested, maybe someone else can comment? But 
for my simple test water system it seems to improve the energy conservation 
considerably. The idea is, I think, to only center the QM molecule in a 
"quantized" manner on equivalent grid points of the (fine DFT?) grid.

To get really good energy conservation you might need to increase your 
cutoff/rel_cutoff too.

Matt

On Wednesday, March 18, 2015 at 11:22:10 AM UTC, Jonggu Jeon wrote:
>
> Dear Dorothea,
>
> Thank you for the invaluable suggestion.  
> While your answer makes perfect sense to me, I just found out that CP2K 
> 2.5.1 does not have option to turn off QMMM/PERIODIC/MULTIPOLE using the 
> section parameter OFF.
> Therefore, CP2K 2.5.1 produces the same (diverging) energy profile whether 
> I set &MULTIPOLE OFF or not.
>
> I will install version 2.6 and try it again.
>
> Best regards,
>
> Jonggu
>
>
> 2015년 3월 18일 수요일 오후 6시 22분 40초 UTC+9, Dorothea Golze 님의 말:
>>
>> 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 <jeon... 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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>>
>>
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