Hi, I have carbon in water system with CHARMM force field( 1-carbon, 2-Hydrogen, 3-Oxygen), I want to switch off the interaction (through the CHARMM ff) between carbon-carbon in that system, and replace the carbon-carbon interaction by a repulsive Lennard-Jones interaction. I have attempted to do this using the pair_style hybrid command in the following way.
pair_style hybrid lj/charmm/coul/long 8 10 lj/cut 3.550053
pair_coeff 2 2 lj/charmm/coul/long 0.046 0.4000135 0.046 0.4000135
pair_coeff 3 3 lj/charmm/coul/long 0.1521 3.150574 0.1521 3.150574
pair_coeff 1 2 lj/charmm/coul/long 0.057 1.975 0.057 1.975
pair_coeff 1 3 lj/charmm/coul/long 0.1032 3.35 0.1032 3.35
pair_coeff 1 1 lj/cut 0.07 3.550053
Is this the correct approach?
Thanks & regards,
Hi, I have carbon in water system with CHARMM force field( 1-carbon,
2-Hydrogen, 3-Oxygen), I want to switch off the interaction (through the
CHARMM ff) between carbon-carbon in that system, and replace the
carbon-carbon interaction by a repulsive Lennard-Jones interaction. I have
attempted to do this using the pair_style hybrid command in the following
way.
pair_style hybrid lj/charmm/coul/long 8 10 lj/cut 3.550053
pair_coeff 2 2 lj/charmm/coul/long 0.046 0.4000135 0.046 0.4000135
pair_coeff 3 3 lj/charmm/coul/long 0.1521 3.150574 0.1521 3.150574
pair_coeff 1 2 lj/charmm/coul/long 0.057 1.975 0.057 1.975
pair_coeff 1 3 lj/charmm/coul/long 0.1032 3.35 0.1032 3.35
pair_coeff 1 1 lj/cut 0.07 3.550053
Is this the correct approach?
depends. it will only work, if you have no (partial) charges on the type 1
atoms. otherwise, there are force contribution from long-range coulomb
through your kspace style, that are not pairwise and thus you cannot turn
off this way.
axel.
Dear Dr. Kohlmeyer
Thank you for your reply. In this simulation the type 1 atoms don’t carry any partial charges so I think it should be fine.
Is it correct to specify the pair coefficients for the lj/charmm/coul/long part in separate lines in the following manner,
pair_coeff 2 2 lj/charmm/coul/long 0.046 0.4000135 0.046 0.4000135
pair_coeff 3 3 lj/charmm/coul/long 0.1521 3.150574 0.1521 3.150574
pair_coeff 1 2 lj/charmm/coul/long 0.057 1.975 0.057 1.975
pair_coeff 1 3 lj/charmm/coul/long 0.1032 3.35 0.1032 3.35
Thanks & regards,
Dear Dr. Kohlmeyer
Thank you for your reply. In this simulation the type 1 atoms don't carry
any partial charges so I think it should be fine.
Is it correct to specify the pair coefficients for the lj/charmm/coul/long
part in separate lines in the following manner,
pair_coeff 2 2 lj/charmm/coul/long 0.046 0.4000135 0.046 0.4000135
pair_coeff 3 3 lj/charmm/coul/long 0.1521 3.150574 0.1521 3.150574
pair_coeff 1 2 lj/charmm/coul/long 0.057 1.975 0.057 1.975
pair_coeff 1 3 lj/charmm/coul/long 0.1032 3.35 0.1032 3.35
i don't have to time to validate inputs. make a test, like everybody else.
axel.