EFFECTIVE HANDLING OF A LARGE CONFIGURATION STATE FUNCTION EXPANSION FOR AN MCSCF STATE AND IMPROVED EFFICIENCY FOR 2-ELECTRON INTEGRAL TRANSFORMATIONS IN MCSCF
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Effective solutions for two difficulties which may be present in MCSCF calculation are discussed: (i) We show how the large configuration state function state expansion case may be handled simply and effectively without the introduction of extraneous projection operators or Lagrange multipliers; (ii) we present a simplified twoelectron integral transformation procedure which significantly reduces the operation count (and hence computational efficiency is increased) for second order and particularly for third order MCSCF procedures. The procedures we introduce use some freedom available in the orthogonal complement Cl space and the virtual orbital space to simplify MCSCF calculations. Copyright 1983 John Wiley & Sons, Inc.