Multi-reference CI

This program exists in several versions, all originating from the program by Dupuis et al. The Cl part in the version by Schmidt et al. is basically the same as in HONDO 8. In the version by Guest and collaborators the Cl may be run by the conventional multi-reference CI-SD algorithm or in the direct Cl fashion. 

Its multi-reference formulation is straightforward, and applicable readily to any type of reference space, complete or otherwise. Apart from the increased size, and therefore increased computational requirements, multi-reference ci is not notably more difficult than the single-reference form, and the ability to use incomplete active spaces can be employed to limit the computational requirements substantially. 

He goes on to compare multi-reference ci with other multi-reference formalisms... 

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