1. To use the external ReaxFF-file, you have to copy the downloaded ReaxFF-file into the Quantumwise installation under lib/python2.7/site-packages/tremolox/potentials/ReaxFF (under Linux, under Windows the path may be slightly different). Then you have to specify the following lines in the script to define the calculator:
potentialSet = TremoloXPotentialSet(name='ReaxFF_AuSCH')
potentialSet.addParticleType(ParticleType(symbol='H', mass=1.00794 * atomic_mass_unit, charge=None, sigma=None, sigma14=None, epsilon=None, epsilon14=None, atomicNumber=1))
potentialSet.addParticleType(ParticleType(symbol='Au', mass=196.967 * atomic_mass_unit, charge=None, sigma=None, sigma14=None, epsilon=None, epsilon14=None, atomicNumber=79))
potentialSet.addParticleType(ParticleType(symbol='C', mass=12.011 * atomic_mass_unit, charge=None, sigma=None, sigma14=None, epsilon=None, epsilon14=None, atomicNumber=6))
potentialSet.addParticleType(ParticleType(symbol='S', mass=32.06 * atomic_mass_unit, charge=None, sigma=None, sigma14=None, epsilon=None, epsilon14=None, atomicNumber=16))
# Add the ReaxFF potential to the potential set
potential = ReaxFFPotential(file='ffield_AuSCH',
qeq=True,
qeqEps=1.000000e-06,
qeqMaxIter=200,
lgvdw=False,
bond_rcut=5.0*Angstrom,
hbond_rcut=7.5*Angstrom,
thb_bond_rcut=0.001000,
thb_bond_rcutsq=0.000010,
multiwell=False,
strict_bondpairs=True)
potentialSet.addPotential(potential)
calculator = TremoloXCalculator(parameters=potentialSet)
The ReaFFpotential options may have to be adapted as needed.
Furthermore, when I tried to run the calculation, the potential file did not work out of the box, because apparently a line is missing. So you have to open the potential file in an Editor and add the following line as the second line:
4 C 6 H 1 S 16 Au 79
so that the beginning of the file reads like
Reactive MD-force field: AuSCH as published in T. T. Jarvi et al., J. Phys. Chem. A, doi: 10.1021/jp201496x
4 C 6 H 1 S 16 Au 79
39 ! Number of general parameters
50.0000 !p(boc1)
9.5469 !p(boc2)
26.5405 !p(coa2)
This is to let the calculator know how many and which atoms it should expect.
However, you are strongly encouraged to test the potential, whether it gives the correct results before using it, because I haven't made any tests!
2. No, it is currently not possible to use more than one ReaxFF-potentials in the same calculator.