Dear Lammp Users,
I am trying to simulate a system by lammps , which include water toluene and hydroxylated silica . However, in most papers , they use CALYFF force field to simulate hydroxylated silica and OPLSAA force field to simulate toluene and water .
How could I use both CLAYFF force field and OPLSAA force field in a system?
In lammps, angle_style harmonic bond_style harmonic pair_style lj/cut/coul/long 12.5 is used to represent the CALYFF force field. however , the pair style of water and toluene is lj/cut/coul/long 10 in generally.
If I use lj/cut/coul/long 12.5 , will it affect other components such as water and toluene?
Do the nonbonded parameters of water and toluene change?
Thank you
zhang
Changing the cutoff from 10.0 to 12.5 is not going to be a big difference, especially since you are using a long-range coulomb solver, so for the coulomb interactions the cutoff only determines where to switch between real space and reciprocal space. and since the attractive part of the LJ interaction scales with O(r^6) there is no much interaction left beyond 10\AA.
What is a bigger concern is the mixing of different force fields in general. Each classical force field has a specific recipe how to generate the parameters and particularly how to balance between the Coulomb and LJ interactions and how to map the charge distributions. When you mix force fields, you have inconsistent interactions and charge distributions. How much of an error it will cause, is difficult to predict. Thus it is advisable to make careful tests to confirm that material properties are unaffected.
Axel.
Axel, Thank you very much for your answer. I will pay attention to it.