W:solvent defining in PCM model



Hi all~
 I am calculating the reaction coordinate in solution.
 For this work, I used Gaussian98 software packages.
 In Gaussian, we can choose some pre-defned solvent for calculation of solvation
 energy. However, I want to use the non-defined solvent for this, such as t-butyl
 alcohol.
 I couldn't find the solution in Gaussian reference mannual and IOps reference
 since there are many internal parameters not allowing the change. Please let me
 know the solution. Alternatively, I really appreciate who recommends the other
 software to solve the problem.