[lammps-users] Notations of the 'cff91_auto' in the pcff.frc file

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1

Dear LAMMPS users,

I have an inquiry regarding the notations used in the ‘cff91_auto’ sections in the pcff.frc file.

In the following example, what do the notations ’ *1 ', ’ * 2 ', … ’ *8 ', and ’ * ’ mean? Many thanks! -Lili

#quadratic_angle cff91_auto

E = K2 * (Theta - Theta0)^2

!Ver Ref I J K Theta0 K2
!— — ----- ----- ----- -------- -------
2.0 2 * c’_ * 120.0000 65.0000
2.0 2 *1 c’_ si_ 120.0000 34.6000
2.0 2 *2 c’_ h_ 110.0000 55.0000
2.0 2 *3 c’_ f_ 120.0000 99.0000
2.0 2 *4 c’_ s’_ 123.0000 80.0000
2.0 2 *5 c’_ s3e_ 120.0000 40.0000
2.0 2 *5 c’_ s4e_ 120.0000 40.0000
2.0 2 *5 c’_ s_ 120.0000 40.0000
2.0 2 *6 c’_ o’_ 120.0000 68.0000
2.0 2 *7 c’_ o_ 110.0000 122.0000
2.0 2 *8 c’_ n3m_ 120.0000 53.5000

2

That is a question for the Materials Studio developers. If you have a license, perhaps it may be documented in the associated documentation.
This is not something LAMMPS deals with and I don’t think that you can even reverse engineer this from the msi2lmp code since that doesn’t handle auto-equivalences.