The Fock-Space Coupled-Cluster Method in the Calculation of Excited State Properties

Our recently developed intermediate Hamiltonian Fock-space coupled-cluster (FS-CC) method with singles and doubles is applied to calculation of equilibrium geometries, harmonic frequencies and adiabatic excitation energies for some excited states of N2 and CO. Due to the intermediate Hamiltonian formulation, which provides a robust computational scheme for solving the FS-CC equations, and the efficient factorization strategy, relatively large basis sets and reference spaces are employed permitting a comparison of calculated properties with experimental data.

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Electronic Spectra and Ionization Potentials of Halogen Oxides Using the Fock Space Coupled-Cluster Method

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20050851 ◽

2005 ◽

Vol 70 (7) ◽

pp. 851-863 ◽

Cited By ~ 2

Author(s):

Nayana Vaval ◽

Prashant Manohar ◽

Sourav Pal

Keyword(s):

Excited States ◽

Fock Space ◽

Ionization Potentials ◽

Cluster Method ◽

Coupled Cluster ◽

Coupled Cluster Method ◽

Excitation Energies ◽

Coupled Cluster Theory ◽

Vertical Detachment Energy ◽

Halogen Oxides

The ionization potentials and excitation energies of halogen monoxides and dihalogen oxides are studied using fully size-extensive Fock space version of multi-reference coupled-cluster theory. The low-lying excited states of ClO-, FO-, Cl2O and F2O are obtained along with the ionization spectra of Cl2O and F2O. The adiabatic electron affinity of ClO, FO and the vertical detachment energy of ClO- and FO- are also presented.

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Effective Hamiltonian and Intermediate Hamiltonian Formulations of the Fock-Space Coupled-Cluster Method

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc20030105 ◽

2003 ◽

Vol 68 (1) ◽

pp. 105-138 ◽

Cited By ~ 6

Author(s):

Leszek Meissner ◽

JarosłaW Gryniaków

Keyword(s):

Schrödinger Equation ◽

Schrodinger Equation ◽

Fock Space ◽

Hamiltonian Formulation ◽

Cluster Method ◽

Coupled Cluster ◽

Effective Hamiltonian ◽

Coupled Cluster Method ◽

Effective Version ◽

Reference Methods

Various aspects of the effective Hamiltonian and intermediate Hamiltonian formulations are discussed in the context of the Fock-space coupled-cluster method. Problems that occur when single-reference methods of solving the Schrödinger equation need to be generalized to the multireference (MR) cases are pointed out. These problems make the generalization nontrivial, especially in the case of the most powerful coupled-cluster (CC) method. It is shown how some specific features of one of the basic MR-CC schemes, the Fock-space CC method, can be used to obtain a simple, yet very effective version of the method. This requires, however, switching from the effective Hamiltonian to the intermediate Hamiltonian formulation. The intermediate Hamiltonian version of the Fock-space CC method is discussed in detail and all its advantages over the standard one are emphasized.

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