I studied on BN simulations in the literature very much and saw no charge
and coulombic interactions that is why I exclude the charges but if you
consider it as a possible deficiency of the model, maybe I should go over
and check if I missed something about that.Besides charge considerations, one thing I cannot understand clearly is
which of the following statements you are exactly saying:a)Using LJ parameters in addition to tersoff and SPC/E is mistake
i am not saying that.
b)Using combining rules for 0-B and 0-N is a mistake
yes, as well as for H-B/H-N.
c)Both of a and b.
to really explain the reason, i would have to give you a lecture on
force field parameterization strategies and methods. this is text book
stuff and this is not the place and neither do i have the time.
Also I want to add that I tried LJ interaction just for cross relations but
not for B-B and N-N interactions because I got inconsistent results for pure
solid BN model with LJ; however, tersoff did well.
i still can't make sense of that. lets see what you have:
- a LJ based model to do BN (but it also likely has bonded interactions)
- a tersoff based model to do BN
- a LJ + charge based model to do water (SPC/E)
what you do *not* have is a model describing the interaction of water
(the SPC/E version, that is) with BN. a) and c) were parameterized
independently and
what you also have not provided is an explanation of how you determine
when your simulation is giving you the right and when the wrong
answer.
As you say parameterization for BN with SPC/E is exaclty what I am looking
for.
but you don't have it and applying mixing rules to two independent
models is not the way to obtain them. besides, why using an inferior
method, when you have access to the real thing: i just did a quick
search on google for molecular dynamics simulations on boron nitride
and water and my first two hits show parameterizations that *do*
include significant partial charges on B and N and, in fact, the
presence of water - as my chemical intuition tells me it should -
enhances those partial charges. the same kind of polarization happens
with CNTs, however, there you can often ignore it if you keep the CNT
structure rigid and include an averaged version of the polarization in
the LJ parameters. since BN is polar, this cannot be done as easily.
now, mixing tersoff with lj/cut/coul/long for this kind of system
consistently is not as simple using pair_style hybrid because of the
long-range coulomb interaction. what you would need is a so-called
ONIOM model approach:
B: compute the BN system only with lj/cut/coul/long + kspace
C: compute the BN system with tersoff w/o kspace
the total forces and energies are then computed as: A - B + C
axel.
p.s.: to pre-empt your next question. the doi for the two papers i
found are: 10.1049/mnl.2009.011 10.1021/jp076747u