8.8. Non-Bond Lennard-Jones (Class 2 Form) Potential

8.8.1. Functional Form

The non-bond Lennard-Jones (Class 2 Form) potential has the functional form:

\(E=\epsilon \left[ 2{{\left( \frac{{R_{min}}}{{{R}_{ij}}} \right)}^{9}}-3{{\left( \frac{{R_{min}}}{{{R}_{ij}}} \right)}^{6}} \right]\)

The force-field parameters for this potential and units are given by:

Equation Symbol Parameter Definition Units
\(\epsilon\) Potential well depth for atom [i] energy/mol
\(R_{min}\) Interatomic cut-off distance for atom [i] length

8.8.2. XML Schema

The XML schema for the non-bond Lennard-Jones (9-6 Form) potential has the following representation (design mode representation using Liquid XML Studio):


The relationship between the equation symbols and XML schema notations are given by:

Parameter Definition Equation Symbol Schema Notation
Atom type of atom [i] (implicit) AtomType
Potential well depth for atom [i] \(\epsilon\) epsilon
Interatomic cut-off distance for atom [i] \(\sigma\) sigma

The general attributes (describing the entire data set) are given by:

General Attributes Cardinality Value/Definition
style Fixed Lennard-Jones (9-6) [Class 2 Form]
formula Fixed epsilon*[2*(Rmin/R)^9-3*(Rmin/R)^6]
epsilon-units Required Enumerations specified in schema
sigma-units Required Enumerations specified in schema
Combining-Rule Required Combining rule for mixed atom types

The specific attributes (attached to each set of parameters) are given by:

Specific Attributes Cardinality Value/Definition
comment Optional Comment attached to parameter set
version Optional Version number of parameter set
reference Optional Reference attached to parameter set

Note that an XML document will be rejected from being entered into the WebFF database if a required attribute is left unspecified.