Uncontracted SOCI methods DGCI

One of the first DGCI codes was developed by Christiansen et al [83], but was limited to diatomic molecules and about 5000 determinants. This code was generalised later to polyatomic molecules independently by Pitzer et al [42] and Balasubramanian [72]. Pitzer et al used Configuration Spin Functions (CSFs) 

In the framework of all-electron schemes, a direct DGCI program based on Slater determinants was initially written by Esser [89]. In this category of codes, Sjovoll et al proposed a generalisation of the direct Cl code LUCIA 

Effective Hamiltonian-based uncontracted SOCI methods (DGCF ) 

One of the first two-step DGCI treatment was implemented in the RCI (Relativistic Cl) code proposed by Balasubramanian [72]. Although his Hamiltonian cannot be written in a simple Bloch-effective Hamiltonian form, it has neverthe- 

Test calculations on excited states of thallium hydride correlating 14 electrons, showed that this technique can accurately describe potential energy curves, but the Cl with single and double substitutions is only treated at the DGCI level and may become heavy if one wants to enlarge the reference space for a better correlation treatment. 

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