Electronic excited states basis functions

This form of the Hamiltonian, using the Frosch and Foley constants, is less useful than the alternative form, written in terms of spherical tensor operators. This is particularly true when the basis functions for the two electronic states are different. For the ground state we use the functions t], A S, I, G N, G, F) and for the excited state //. A N, S,./ ./. /. / ). As we have seen in chapters9 and 10, the appropriate effective Hamiltonian when the excited state basis functions are used is... 

M. Schreiber, M.R. Silva-Junior, S.P.A Sauer, W. Thiel, Benchmarks for electronically excited states CASPT2, CC2, CCSD, and CCS, J. Chem. Phys. 128 (2008) 134110 M.R. Sflva-Junior, M. Schreiber, S.P.A. Sauer, W. Thiel, Benchmarks for electronically excited states Time-dependent density functional theory and density functional theory based multireference configuration interaction, J. Chem. Phys. 129 (2008) 104103 S.P.A. Sauer, M. Schreiber, M.R. Silva-Junior, W. Thiel, Benchmarks for Electronically Excited States A Comparison of Noniterative and Iterative Triples Corrections in Linear Response Coupled Cluster Methods CCSDR(3) versus CCS, J. Chem. Theory Comput. 5 (2009) 555 M.R. Silva-Junior, S.P.A. Sauer, M. Schreiber, W. Thiel, Basis set effects on coupled cluster benchmarks of electronically excited states CCS, CCSDR(3) and CC2, Mol. Phys. 108 (2010) 453 M.R. Silva-Junior, M. Schreiber, S.P.A. Sauer, W. Thiel, Benchmarks of electronically excited states basis set effects on CASPT2 results, J. Chem. Phys. 133 (2010) 174318. 

If several electronically excited states are relevant for describing the photodissociation then one or more of the Rydberg orbitals of the molecule must be included in the (CAS) [13], As the number of orbitals and electrons increases in the CAS, the computational time increases dramatically. In order to obtain accurate potential energy surfaces for the excited electronic states, one must include diffuse functions in the basis set [4], For heavier atoms, a relativistic effective core potential (ECP) can be used to treat the scalar relativistic effects. The ECP basis sets have been developed by several research groups [15,16] and have been implemented in most of the standard electronic structure programs. 

We have also added a method of calculating improved virtual orbitals. Our use of this procedure for N electron excited state virtual orbitals (8l) in the framework of the SCF calculation of the N-l electron problem closely resembles those proposed by Huzinaga (82). We have also investigated Huzinagafs recent method for improved virtual orbitals in the extended basis function space (83) This is also a useful procedure where there are convergence problems for the Hartree-Fock calculations for the N-electron occupied space of the excited states. This should also be helpful in optimizing virtual orbitals to use them in perturbation theory expressions. 

The configuration interaction (Cl) procedure is one of the commonly used methods for determination of electronically excited states [30]. Starting from a finite set l/j of orthonormal one-electron basis functions (which can be either Hartree-Fock (HF) or canonical multiconfigurational self-consistent field (MCSCF) orbitals) [30], a subset of all possible antisymmetrized products have to be constructed ... 

There have not been too many studies, in particular using highly correlated wave functions, of the basis set and correlation requirements for the direct spin-spin interaction to the zero-field splitting. For the spin-orbit contribution, the basis set requirements follow to a large extent those applicable for the spin-orbit correction to the g tensor. Otherwise, an accurate description of the relevant electronic excited states contributing to the spin-orbit contribution is required, which by itself may be a challenge in the case of transition-metal complexes (Bolvin 2006). 

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