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19.5.2 Defining the starting CI coefficients

MULTI normally obtains configuration mixing coefficients by a robust eigenvector solver that converges on the lowest eigenvalues, and applies a phase convention such that the largest coefficient is forced to be positive. For most purposes, this approach is satisfactory.

Sometimes one wants a guarantee that the CI vector is phase matched to that of a previous geometry. This can be achieved by using SAVE,CI=record.file (see section 19.5.5) in the first job, and in the restart,


The phase convention applied for the rest of the calculation is then that, for each optimised state, the largest coefficient in the original CI vector defines the sign of the corresponding coefficient in the optimised vector. 2017-12-12