Using hybrid command, return different v_enonbond value

Dear LAMMPS developers.

I want to use “lj/cut/coul/long” and “morse” to the non-bonding interaction same time.

For understand the hybrid command, I simulated using following (1)(2) .in file.

The other descriptions are the same and .data file has same velocity values.

I think (1)(2) return same v_enonbond values.

But,

(1) Rturned v_enonbond = 3988.41 epsilon (0step)

(2) Rturned v_enonbond = 4842.37 epsilon (0step)

Why values are different. Am I mistaking somewhere?

Please tell me.

Yuki.Tanaka

-------------------------.in file-------------------------

(1) lj/cut/coul/long

kspace_style pppm 1e-4

pair_style lj/cut/coul/long 8.908987 11.303883

pair_coeff 1 1 0.061 3.118146 7.795364

pair_coeff 1 2 0.101833 3.059079 7.647697

pair_coeff 1 3 0.128335 2.850878 7.127194

(2) lj/cut/coul/long + morse(cutoff =0) using hybrid

kspace_style pppm 1e-4

pair_style hybrid lj/cut/coul/long 8.908987 11.303883 morse 5.967525

pair_coeff 1 1 lj/cut/coul/long 0.061 3.118146 7.795364

pair_coeff 1 2 lj/cut/coul/long 0.101833 3.059079 7.647697

pair_coeff 1 3 lj/cut/coul/long 0.128335 2.850878 7.127194

pair_coeff 4 10 morse 0.1259 2.0502 2.7251 0 #cutoff =0

Because “hybrid” overwrites old pair_coeff with new ones. In your script, 4-10 interaction in case 1 is a lj/cut/coul/long with coefficients (my guess since you cut it out…), however in case 2, 4-10 interaction is morse (effectively zero since you have zero cutoff).

You would want to use “hybrid/overlay” in this case.

Ray

Dear Ray

Thank you for your answering.

Sorry, my explanation was insufficient・・・.

In case 1 and 2,

(1)pair_coeff 4 10 0 0 0.001 # 4 means hydrogen

and

(2)pair_coeff 4 10 lj/cut/coul/long 0 0 0.001 # 4 means hydrogen

So, there are no 4-10 interactons in both cases.

Nevertheless, the values are different.

I tried using hybrid/overlay command once, but the values was not changed.

Best regards.

Yuki. Tanaka

-------------------------.in file(added 4-10)-------------------------

(1) lj/cut/coul/long

kspace_style pppm 1e-4

pair_style lj/cut/coul/long 8.908987 11.303883

pair_coeff 1 1 0.061 3.118146 7.795364

pair_coeff 1 2 0.101833 3.059079 7.647697

pair_coeff 1 3 0.128335 2.850878 7.127194

pair_coeff 4 10 0 0 0.001 # 4 means hydrogen

(2) lj/cut/coul/long + morse(cutoff =0) using hybrid

kspace_style pppm 1e-4

pair_style hybrid lj/cut/coul/long 8.908987 11.303883 morse 5.967525

pair_coeff 1 1 lj/cut/coul/long 0.061 3.118146 7.795364

pair_coeff 1 2 lj/cut/coul/long 0.101833 3.059079 7.647697

pair_coeff 1 3 lj/cut/coul/long 0.128335 2.850878 7.127194

pair_coeff 4 10 lj/cut/coul/long 0 0 0.001 # 4 means hydrogen

pair_coeff 4 10 morse 0.1259 2.0502 2.7251 0 #cutoff =0

2016/02/23 1:09、Ray Shan <rayshan819@…24…> :

Then we can’t really tell from these pieces of incomplete information. You would have to attach your full input script and data.

Ray