Atom -Atom interactions File

This is a required file and it describes the atom-atom interaction parameters. The file consists of a number of columns separated by space(s). Multiple force models may be defined for each atom-atom pair, but each must exist on its own line. The particular force model that is used during the simulation is defined in the molecule-molecule interaction file(). The file is parsed by the routine ``pairmodel'' The meaning of each column is explained below.

This file needs to have entries only if BASIC was used in the molecule-molecule interaction file.

columns 1, 2

The name of the atom pair.

column 3

The name of the forcefield we want to use for pairwise interactions. Options are LJ BUCK HS WFCOUL etc. If we don't want the atoms to interaction then the value in this column should be ``OFF''.

columns4 -

Column 4 onwards are fields specific to the forcefield type given in column 3. See the examples in the tests directlry.

Note: Every atom-atom pair in the simulation has to have an entry in the atom-atom file.

Sample atom-atom file

## Coulombic, charges were specified when u defined teh molecule
## If you want some other charges to be used 
## then use the format ``Carbon    Oxygen    COUL Q1@0.82 Q2@-1.4''
Oxygen    Oxygen    COUL
Carbon    Carbon    COUL
Oxygen    Carbon    COUL
Hydrogen  Carbon    COUL
Hydrogen  Oxygen    COUL
Hydrogen  Hydrogen  COUL

## Lennard Jones
Methyl    Methyl    LJ SIG@3.77   EPS@98.1     HICUT@13.0  LOCUT@0.5 
Methyl    Methyl    LJ SIG@3.77   EPS@98.1     HICUT@13.0  LOCUT@0.5 
Carbon    Methyl    LJ SIG@LBMIX   EPS@LBMIX     HICUT@13.0  LOCUT@0.5

Silicon   Silicon   OFF
Oxygen    Oxygen    OFF
Methane   Methane   LJ SIG@3.730  EPS@148.013  HICUT@13.0 LOCUT@0.01
CF4       CF4       LJ SIG@4.662  EPS@134.048  HICUT@13.0 LOCUT@0.01
Methane   CF4       LJ SIG@LBMIX  EPS@LBMIX  HICUT@13.0 LOCUT@0.01

## Buckingham potentials
Methyl    Methyl    BUCK A@1550.95 C@0.0 RHO@0.30017 HICUT@10.0 LOCUT@0.01
Methylene Methylene BUCK A@1550.95 C@0.0 RHO@0.30017 HICUT@10.0 LOCUT@0.01
Methyl    Methylene BUCK A@1550.95 C@0.0 RHO@0.30017 HICUT@10.0 LOCUT@0.01
Methane   Oxygen    OFF
Methane   Silicon   OFF
CF4 	  Oxygen    OFF
CF4 	  Silicon   OFF
################### Benzene Potentials #####################
Carbon    Carbon   BenzPot A@698828.9 B@569.7  C@8.389  D@-0.3346 Rhigh@13.0 Rlow@5.0
Carbon    Hydrogen BenzPot A@91826.0  B@112.26 C@-8.389 D@0.3346  Rhigh@13.0 Rlow@5.0

## end of atom-atom-file