Soft-Core Pseudopotentials and Separability

Sophisticated procedures have been devised for this purpose, in the early nineties27,117-120 relying on special expansion functions for the fy of equation 

However, in particular for DFT-based applications in solid-state theory, a small expansion length in equation (21) is desirable, to keep the computational effort within manageable limits. Such a small expansion should at least include the functions 

At the end of this section, we want to mention a very recent approach,131 which has much in common with the other schemes just described (applicability 

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