[lammps-users] Hybrid Function Regarding

Dear Sir,

I already posted this, but thought that may perhaps be not understood. I want to simulate 7 types of atoms as follows:

Atoms 1, 2, 3 are Silicon
Atoms 4,5,6 are Carbon

& Atom 7 is Oxygen

I tried to use the hybrid potential in the following manner but received the error.

pair_style hybrid/overlay tersoff
pair_coeff * * tersoff SiCGe.tersoff Si(D) Si(D) Si(D) C C C NULL
pair_coeff * * tersoff SiO.tersoff Si Si Si NULL NULL NULL O

Can u help me rectify the error.

Regards,
Saurav

Dear Sir,

I already posted this, but thought that may perhaps be not understood. I
want to simulate 7 types of atoms as follows:

Atoms 1, 2, 3 are Silicon
Atoms 4,5,6 are Carbon

& Atom 7 is Oxygen

I tried to use the hybrid potential in the following manner but received the
error.

pair_style hybrid/overlay tersoff
pair_coeff * * tersoff SiCGe.tersoff Si(D) Si(D) Si(D) C C C NULL
pair_coeff * * tersoff SiO.tersoff Si Si Si NULL NULL NULL O

Can u help me rectify the error.

you cannot do that.

the documentation states that clearly.

if you want to use tersoff on all those atom types, you need
_one_ tersoff potential file that has all the permutations of
many body interactions.

if you can guarantee that oxygens never come within the
cutoff distance to carbons, you could set the potential
entries for O-C containing interactions to zero, but that
requires a _lot_ of care.

axel.

Sincere thanks for prompt reply. Is there any other pot. available that can be used along with tersoff as a hybrid for Oxygen.

Sincere thanks for prompt reply. Is there any other pot. available that can
be used along with tersoff as a hybrid for Oxygen.

check the literature.

you cannot mix and match potentials at will, particularly not with
many-body potentials. using a hybrid potential style with manybody
potentials has implications that have been discussed many, many
times on this list.

if you want to do all those atoms with tersoff, you have to "find" the
parameters or learn how to generate them, or after proving that you
can ignore the permutations containing C and O, learn how to change
a potential file without messing it up.

there ain't no escape from the blues,
    axel.

I have set the value of O-C Interaction as zero

C O O 0 0 0.0 0 0 0 0.00000 0.0000000 0.0000 000.00 0 0 0.0000 0000.0
C C O 0 0 0.0 0 0 0 0.00000 0.0000000 0.0000 000.00 0 0 0.0000 0000.0
C O C 0 0 0.0 0 0 0 0.00000 0.0000000 0.0000 000.00 0 0 0.0000 0000.0

O C C 0 0 0.0 0 0 0 0.00000 0.0000000 0.0000 000.00 0 0 0.0000 0000.0
O C O 0 0 0.0 0 0 0 0.00000 0.0000000 0.0000 000.00 0 0 0.0000 0000.0
O O C 0 0 0.0 0 0 0 0.00000 0.0000000 0.0000 000.00 0 0 0.0000 0000.0

but it is showing Illegal Tersoff Parameter.

P.S. You mentioned about O-C entries what about S-O-C entries.

you can just set stuff to zero without knowing what you are changing.

smarten up!

axel.