Possible error in Gay-Berne potential formulation in manual

Dear Users,

In the documentation page of GayBerne potential there is a link to a pdf file containing further information about the formulation. I have found some discrepancies between the file and the citation it included (Evaraers), in the definition of parameters \chi, B_{12} and E_1 (E_2).

In the paper,

(1) E_1=diag(\epsilon_a1^(-1/\mu),\epsilon_b1^(-1/\mu),\epsilon_c1^(-1/\mu)),

(2) B_12=A_1 E_1 A_1^T+A_2 E_2 A_2^T, and

(3) \chi=[r_12 B_12 r_12^T]^\mu.

In lammps explanation,

(1) E_1=diag(\epsilon_a1,\epsilon_b1,\epsilon_c1),

(2) B_12=A_1 E_1^2 A_1^T+A_2 E_2^2 A_2^T, and

(3) \chi=[r_12 B_12 r_12^T]^\mu

In the former, the well depth is proportional to the parameters \epsilon_i, however in the latter, it is inversely proportional to some exponential of them. The latter formulation cannot be found anywhere else and is incompatible to what is being done in the source code according to my understanding. Could anyone please check it up?

Thanks a lot!


Patrick Hejian Zhu

This is a Q for Mike Brown, CCd.


Hi Patrick,

You are correct. The epsilon_i_. parameters specified in LAMMPS are the well-depths for the side-to-side, end-to-end, etc. interactions (not inversely proportional as listed in the extra documentation). I will correct the document.

Very sorry for this confusion.

Thanks! - Mike

Note: A possible issue in pair_style gayberne was reported recently:


I don’t think anybody is certain that this is a bug, but I’m taking advantage of the renewed attention directed at this useful pair style. If anyone has an opinion on this, I’m curious to hear it. I hope I’m not wasting people’s time.

Thanks a lot for your help.

All the Best,