hybrid potential

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1

Hello,

I have encountered a problem about the hybridization of lj and tersoff potentials.
I have two kinds of atoms C and Si labeled as 1 and 2 respectively. I would like to have tersoff potential for C-C and Si-Si interactions and lj potential for C-Si.

Here is part of my input file:

pair_style lj/cut 3.0

pair_coeff * * 0.00284 3.4
neigh_modify exclude type 1 1
neigh_modify exclude type 2 2

pair_coeff * * SiCGe.tersoff C NULL
pair_coeff * * SiCGe.tersoff NULL Si

Is this correct? I got the error appearing as:
ERROR: Expected floating point parameter in input script or data file (…/pair_lj_cut.cpp:458)

Any comments are welcome.

Thanks a lot!
Yuezhou Wang

2

I don’t see why you’re getting that error with those lines.
I expect the error is coming from some other line
you are not showing.

But to do what you want with Tersoff and LJ, you
need to use pair_style hybrid. Its doc page has

instructions on how to do what you want. I think
you will need to specify tersoff twice, once for
C NULL (type 1) and once for NULL Si (type 2),
then lj/cut for 1/2 interactions.

Steve

3

Hello,

I have encountered a problem about the hybridization of lj and tersoff
potentials.
I have two kinds of atoms C and Si labeled as 1 and 2 respectively. I would
like to have tersoff potential for C-C and Si-Si interactions and lj
potential for C-Si.

Here is part of my input file:

partial inputs are almost always problematic, since quite often the
problem is elsewhere.

pair_style lj/cut 3.0
pair_coeff * * 0.00284 3.4
neigh_modify exclude type 1 1
neigh_modify exclude type 2 2

pair_coeff * * SiCGe.tersoff C NULL
pair_coeff * * SiCGe.tersoff NULL Si

Is this correct? I got the error appearing as:

of course not. please read the documentation:
http://lammps.sandia.gov/doc/pair_hybrid.html

ERROR: Expected floating point parameter in input script or data file
(../pair_lj_cut.cpp:458)

please check your input whether characters are actual ASCII
characters. if you cut-n-paste from some webbrowser or PDF viewer,
this often is not the case.

Any comments are welcome.

please make a better effort to read the documentation, study the
bundled examples and search the mailing list archive and the web for
suitable examples and discussions on similar subjects. already the
first step should have guided you to the right information.

axel.