# help

hello
What is definition of A&B coefficients in the bottom. and for methane and nitrogen A and B equal …? . Or how can I determine them

``````pair_style lj/cut 2.5
pair_coeff * * A B
``````
``````thanks
``````

hello
What is definition of A&B coefficients in the bottom. and for methane and
nitrogen A and B equal ....?

http://lammps.sandia.gov/doc/pair_lj.html

. Or how can I determine them

please have a look into a textbook on MD where it explains how force
field parameters are determined.
please note that parameters are generally specific for a limited range
of thermodynamic states (temperature, pressure) and there is thus not
going to be *the* set of parameters.

axel.

I looked at the book

b= sigma
I know that how calculated for many atoms

but I do not understand that What’s scale
Nm or Å (Sigma)
K or J (epsilon)
<<>>

they are Absolute or relative؟
i read manual and md book but
I did not see the explanation About coeff and LAMMPS
\$\$\$\$\$\$\$\$\$\$\$
If you can tell me a “”“book”""""
\$\$\$\$\$\$\$\$\$\$\$

What is the relationship between the data and the coefficients?
1: 1
1:m*1
or n.02>>>> m???

thank u very very very

I looked at the book

a: epsilon
b= sigma
I know that how calculated for many atoms

but I do not understand that What's scale
Nm or Å (Sigma)
K or J (epsilon)
<<<Exclusively for the coefficients used in LAMMPS>>>

they are Absolute or relative؟

they can be either.

i read manual and md book but
I did not see the explanation About coeff and LAMMPS

there is:

http://lammps.sandia.gov/doc/units.html

you need to read more carefully.