Example: The effect of specifying atom types, or not

Whether or not you specify the ForceField.Type on input (via atom attributes) makes a difference for the hybrid engine using a ForceField sub engine.

If you do, then for all regions these atom types will be used.

If you do not specify them, then for each region independently the atom typing will done automatically (if possible).

Download AtomAttributes.run

#!/bin/bash

export NSCM=1

# Here we show the role played by the  (ForceField.Type) atom attribute

# on purpose we specify a strange type for the carbon atoms "C_2" (nonsensical for any of the regions)

# we also show that capitalization does not matter for the keys ForceField.Charge and Type.
# For the values, such as C_R the case matters


# In the first run we specify in the input ForceField.Type
# The result is that for all regions this will be used, and the type for C is always C-2
# -------------------
# region mol.  C-type
# -------------------
#  MM    CH3   C_2
#  *     C2H6  C_2
#  QM    CH4   C_2 
#--------------------


export AMS_JOBNAME=type=inp.cap=none

rm -rf $AMS_JOBNAME.results

$AMSBIN/ams <<eor

Task GeometryOptimization

Properties Gradients=yes

System
    Atoms
        C -1.559601 -1.234340  0.000641 region=QM forcefield.charge=-0.27  forcefield.type=C_2
        H -1.898371 -0.303860  0.503021 region=QM ForceField.Charge=0.09   ForceField.Type=H_
        H -2.034545 -2.108050  0.494609 region=QM ForceField.Charge=0.09   ForceField.Type=H_
        H -1.869847 -1.205955 -1.065139 region=QM ForceField.Charge=0.09   ForceField.Type=H_
        C -0.047661 -1.348892  0.094039 region=MM ForceField.Charge=-0.27  ForceField.Type=C_2
        H  0.427282 -0.475182 -0.399929 region=MM ForceField.Charge=0.09   ForceField.Type=H_
        H  0.291107 -2.279373 -0.408341 region=MM ForceField.Charge=0.09   ForceField.Type=H_
        H  0.262583 -1.377277  1.159819 region=MM ForceField.Charge=0.09   ForceField.Type=H_
    End
    GuessBonds True
End


Engine Hybrid
    QMMM qmRegion=QM qmEngineID=DFTB mmEngineID=ForceField
    
    Engine DFTB
    EndEngine

    Engine ForceField
    EndEngine

EndEngine

eor

#  Not specifying the types, they will be guessed independently for all regions

# -------------------
# region mol.  C-type
# -------------------
#  MM    CH3   C_R
#  *     C2H6  C_3
#  QM    CH4   C_3 
#--------------------

export AMS_JOBNAME=type=none.cap=none

rm -rf $AMS_JOBNAME.results

$AMSBIN/ams <<eor

Task GeometryOptimization

Properties Gradients=yes

System
    Atoms
        C -1.559601 -1.234340  0.000641 region=QM forcefield.charge=-0.27
        H -1.898371 -0.303860  0.503021 region=QM ForceField.Charge=0.09 
        H -2.034545 -2.108050  0.494609 region=QM ForceField.Charge=0.09 
        H -1.869847 -1.205955 -1.065139 region=QM ForceField.Charge=0.09 
        C -0.047661 -1.348892  0.094039 region=MM ForceField.Charge=-0.27
        H  0.427282 -0.475182 -0.399929 region=MM ForceField.Charge=0.09 
        H  0.291107 -2.279373 -0.408341 region=MM ForceField.Charge=0.09 
        H  0.262583 -1.377277  1.159819 region=MM ForceField.Charge=0.09 
    End
    GuessBonds True
End


Engine Hybrid
    QMMM qmRegion=QM qmEngineID=DFTB mmEngineID=ForceField
    
    Engine DFTB
    EndEngine

    Engine ForceField
    EndEngine

EndEngine

eor


# The last two runs are mostly a technical test
# We change the capping setup, but that influences only the capping atom

export AMS_JOBNAME=type=inp.cap=inp

rm -rf $AMS_JOBNAME.results

$AMSBIN/ams <<eor

Task GeometryOptimization

Properties Gradients=yes

System
    Atoms
        C -1.559601 -1.234340  0.000641 region=QM forcefield.charge=-0.27  forcefield.type=C_2
        H -1.898371 -0.303860  0.503021 region=QM ForceField.Charge=0.09   ForceField.Type=H_
        H -2.034545 -2.108050  0.494609 region=QM ForceField.Charge=0.09   ForceField.Type=H_
        H -1.869847 -1.205955 -1.065139 region=QM ForceField.Charge=0.09   ForceField.Type=H_
        C -0.047661 -1.348892  0.094039 region=MM ForceField.Charge=-0.27  ForceField.Type=C_2
        H  0.427282 -0.475182 -0.399929 region=MM ForceField.Charge=0.09   ForceField.Type=H_
        H  0.291107 -2.279373 -0.408341 region=MM ForceField.Charge=0.09   ForceField.Type=H_
        H  0.262583 -1.377277  1.159819 region=MM ForceField.Charge=0.09   ForceField.Type=H_
    End
    GuessBonds True
End


Engine Hybrid
    QMMM qmRegion=QM qmEngineID=DFTB mmEngineID=ForceField
    
    Engine DFTB
    EndEngine

    Engine ForceField
    EndEngine

    Capping
        CappingElement Li
        AtomicInfoForCappingAtom ForceField.Type=Li
    End

EndEngine

eor

export AMS_JOBNAME=type=none.cap=inp

rm -rf $AMS_JOBNAME.results

$AMSBIN/ams <<eor

Task GeometryOptimization

Properties Gradients=yes

System
    Atoms
        C -1.559601 -1.234340  0.000641 region=QM forcefield.charge=-0.27 
        H -1.898371 -0.303860  0.503021 region=QM ForceField.Charge=0.09  
        H -2.034545 -2.108050  0.494609 region=QM ForceField.Charge=0.09  
        H -1.869847 -1.205955 -1.065139 region=QM ForceField.Charge=0.09  
        C -0.047661 -1.348892  0.094039 region=MM ForceField.Charge=-0.27 
        H  0.427282 -0.475182 -0.399929 region=MM ForceField.Charge=0.09  
        H  0.291107 -2.279373 -0.408341 region=MM ForceField.Charge=0.09  
        H  0.262583 -1.377277  1.159819 region=MM ForceField.Charge=0.09  
    End
    GuessBonds True
End


Engine Hybrid
    QMMM qmRegion=QM qmEngineID=DFTB mmEngineID=ForceField
    
    Engine DFTB
    EndEngine

    Engine ForceField
    EndEngine

    Capping
        CappingElement Li
        AtomicInfoForCappingAtom ForceField.Type=Li
    End

EndEngine

eor