Complete active space CASSCF

Xe and Rn elements Table 1.3. The scalar spin-free lOTC complete active space CASSCF/CASPT2 method was used followed by the restricted active space state-interaction (RASSI) method with the use of the atomic mean-filed spin-orbit (SO) integrals AMFI. 

Besides the traditional scheme, AIMD using semiempirical, Hartree-Fock, generalized valence bond (GVB), complete active space (CASSCF), and configuration interaction (CI) electronic structure methods have been realized. Several different variations concerning the basis set... 

Roos B O, Taylor P R and Siegbahn P E M 1980 A complete active space SCF method (CASSCF) using a density matrix formulated super-CI approach Chem. Phys. 48 157-73... 

An MCSCF calculation in which all combinations of the active space orbitals are included is called a complete active space self-consistent held (CASSCF) calculation. This type of calculation is popular because it gives the maximum correlation in the valence region. The smallest MCSCF calculations are two-conhguration SCF (TCSCF) calculations. The generalized valence bond (GVB) method is a small MCSCF including a pair of orbitals for each molecular bond. 

In this exercise, we will introduce the Complete Active Space Multiconfiguration SCF (CASSCF) method, using it to compute the excitation energy for the first excited state of acrolein (a singlet). The CIS job we ran in Exercise 9.3 predicted an excitation energy of 4.437 eV, which is rather for from the experimental value of 3.72 eV. We ll try to improve this prediction here. 

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