Pair_style question

Hi all,

I am trying to run a simulation with e3b water model and tersoff potential (water with a graphene surface). According to the manual I am trying to use the Tainter 2015 e3b parameters with the hybrid/overlay pair style. (with pair_coeff * * e3b preset 2015) But to use the tersoff potential I have to use the hybrid pair style (with pair_coeff * * SiC.tersoff Si C Si).
Can anyone let me if there is a way to do this so that I can run e3b water with the tersoff potential?

Thank you.

Regards,
Visal

you can use hybrid/overlay instead of hybrid. you just need to be more careful about not double counting interactions. for the most part the two are the same code, just one rejects configurations where interactions between pairs of atoms are computed multiple times, while the other does not.

of course there is the additional complication that you also need to find and set a pair_style and parameters for the interaction between the two subsystems (water and solid), which needs to be using a pair-wise additive potential.

axel.

Dear Dr. Axel,

Thank you so much for your reply. I have another question related to this. I am using pair styles and coefficients as follows with water having e3b (atom type 1 and 2), graphene (atom type 3) with tersoff and mixing with oplsaa. The C.tersoff havs only parameters for C-C-C for tersoff.

#set up potential
pair_style hybrid/overlay e3b 1 lj/cut/tip4p/long 1 2 1 1 0.1546 8.5 hybrid lj/cut/coul/long 8.5 8.5 tersoff

#tersoff
pair_coeff * * tersoff C.tersoff NULL NULL C

#2B
pair_coeff 1 1 lj/cut/tip4p/long 0.1852 3.1589
pair_coeff 1 2 lj/cut/tip4p/long 0.0 0.0
pair_coeff 1 3 lj/cut/coul/long 0.1016 3.2772
pair_coeff 2 2 lj/cut/tip4p/long 0.0 0.0
pair_coeff 2 3 lj/cut/coul/long 0.0 0.0

#e3b
pair_coeff * * e3b preset 2015

I want to know the following.

  1. With the above definitions of the pairwise potentials, does the tersoff poentental apply just to the C (atom type 3) atoms and the e3b adds only to the water atoms (type 1 and 2)? This is what I understood from the manual and just wanted to make sure that I am not overriding or incorrectly applying tersoff and e3b to different atom types other than the ones that I expect.

Thank you.

Regards,
Visal

You can easily confirm this yourself by selectively enabling only individual parts of the interactions an writing out the forces for one step and comparing the result with the case of all being active.
Axel

Dear Dr. Axel,

Thank you for the suggestion. I will check it out.

Regards,
Visal