[lammps-users] about the pair_style hybrid

Hello

I have a problem about the pair_style hybrid command. When I run the following code
there is always ERROR: Pair coeff for hybrid has invalid style
I hope there is the LJ potential between atom type 1 and atom type 2.
There is the tersoff potential among atom type 1 itself.
There is the tersoff potential among atom type 2 itself.
I have already put the SiCGe.tersoff in the working directory.

This is the code in.pingyi

Hi Anderson,

Are you trying to simulate Carbon atoms only? If that’s the case you might only need to use the regular pair_style tersoff.

pair_style tersoff
pair_coeff * * SiCGe.tersoff C

Since all your atoms are C that should take care of all the interactions in your data file.

Jaime

The following lines are wrong:

pair_coeff 1 1 SiCGe.tersoff C
pair_coeff 2 2 SiCGe.tersoff C

If you want to have type 1 atoms interacting amongst themselves with a
Tersoff potential, the same with type 2 atoms and a LJ interaction
between type 1 and 2 atoms, then the only way this can work, that I
can think of, is to have a Tersoff potential file for the two type of
atoms with entries:

C(1) C(1) C(1) 3.0 1.0 0.0 3.8049e4 4.3484 -0.57058 0.72751
1.5724e-7 2.2119 346.7 1.95 0.15 3.4879 1393.6
C(2) C(2) C(2) 3.0 1.0 0.0 3.8049e4 4.3484 -0.57058 0.72751
1.5724e-7 2.2119 346.7 1.95 0.15 3.4879 1393.6
C(1)

The following lines are wrong:

pair_coeff 1 1 SiCGe.tersoff C
pair_coeff 2 2 SiCGe.tersoff C

If you want to have type 1 atoms interacting amongst themselves with a
Tersoff potential, the same with type 2 atoms and a LJ interaction
between type 1 and 2 atoms, then the only way this can work, that I
can think of, is to have a Tersoff potential file for the two type of
atoms with entries like:

C(1) C(1) C(1) 3.0 1.0 0.0 3.8049e4 4.3484 -0.57058 0.72751
1.5724e-7 2.2119 346.7 1.95 0.15 3.4879 1393.6
C(2) C(2) C(2) 3.0 1.0 0.0 3.8049e4 4.3484 -0.57058 0.72751
1.5724e-7 2.2119 346.7 1.95 0.15 3.4879 1393.6

C(1) C(2) C(2) 3.0 1.0 0.0 3.8049e4 4.3484 -0.57058 0.72751
1.5724e-7 2.2119 0 1.95 0.15 3.4879 0
C(1) C(2) C(1) 3.0 1.0 0.0 3.8049e4 4.3484 -0.57058 0.72751
1.5724e-7 2.2119 0 1.95 0.15 3.4879 0
C(1) C(1) C(2) 3.0 1.0 0.0 3.8049e4 4.3484 -0.57058 0.72751
1.5724e-7 2.2119 0 1.95 0.15 3.4879 0

C(2) C(1) C(1) 3.0 1.0 0.0 3.8049e4 4.3484 -0.57058 0.72751
1.5724e-7 2.2119 0 1.95 0.15 3.4879 0
C(2) C(1) C(2) 3.0 1.0 0.0 3.8049e4 4.3484 -0.57058 0.72751
1.5724e-7 2.2119 0 1.95 0.15 3.4879 0
C(2) C(2) C(1) 3.0 1.0 0.0 3.8049e4 4.3484 -0.57058 0.72751
1.5724e-7 2.2119 0 1.95 0.15 3.4879 0

where you set to zero the repulsive and attractive terms between type
1 and 2 atoms.

Regards,
Zhun-Yong

The following lines are wrong:
pair_coeff 1 1 SiCGe.tersoff C

The reason it is wrong is you need the word "tersoff" in it.

As also indicated, the only way to have 1-1 = 2-2 = tersoff,
but 1=2 = lj/cut is to use pair_style hybrid/overlay and
defined all 3 interactions as tersoff:

pair_coeff * * tersoff file C C

and 1-2 as LJ

pair_coeff 1 2 lj/cut ...

and then have your Tersoff file turn off the interactions between 1-2.

Steve