Additional Sources of Free Energy
In some cases, the expression for the free energy can include other sources. It is possible to incorporate these by modifying
Equation 11-11
:
(11-13)
where
f
is a user-defined free energy (SI unit: J/m
3
).
The expression for the external free energy must be manually differentiated with respect to
and then entered into the
field. In most cases, the external free energy is zero.
and then entered into the 
field. In most cases, the external free energy is zero.