3.4. Morse Bond¶
3.4.1. Functional Form¶
The Morse bond potential has the functional form:
\(E=D{{\left[ 1-{{e}^{-\alpha ({{R}_{ij}}-{{R}_{0,ij}})}} \right]}^{2}}\)
The force-field parameters for this potential and units are given by:
| Equation Symbol | Parameter Definition | Units |
| \(D\) | Depth of the potential well | energy |
| \(\alpha\) | Stiffness parameter | inverse length |
| \(R_{0,ij}\) | Equilibrium bond length for atoms [i,j] | length |
3.4.2. XML Schema¶
The XML schema for the Morse bond 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] | \(i\) | AT-1 |
| Atom type of atom [j] | \(j\) | AT-2 |
| Depth of the potential well | \(D\) | D |
| Stiffness parameter | \(\alpha\) | A |
| Equilibrium bond length for atoms [i,j] | \(R_{0,ij}\) | R0 |
The general attributes (describing the entire data set) are given by:
| General Attributes | Cardinality | Value/Definition |
| style | Fixed | Morse |
| formula | Fixed | D*[(1-exp(-A(R-R0))]^2 |
| D-units | Required | Enumerations specified in schema |
| A-units | Required | Enumerations specified in schema |
| R0-units | Required | Enumerations specified in schema |
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.