Journal ArticleDOI
A spin-adapted linear response theory in a coupled-cluster framework for direct calculation of spin-allowed and spin-forbidden transition energies
Somnath Ghosh,Debashis Mukherjee,Subir Bhattacharyya +2 more
- Vol. 72, Iss: 1, pp 161-176
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TLDR
In this paper, a spin-adapted linear response theory in a coupled-cluster framework was proposed to calculate the spin-allowed and spin-forbidden transition energies from a single methodology.Abstract:
In this paper, we have spin-adapted our recently formulated linear response theory in a coupled-cluster framework. This allows us to calculate directly both the spin-allowed and the spin-forbidden transition energies from a single methodology. We have introduced rank-zero and rank-one spin operators to construct excitation operators for singlet-singlet and singlet-triplet transitions respectively and utilised the graphical methods of spin algebra to integrate the spin variables. It has been shown how a suitable parameterisation of the reduced Hugenholtz matrix elements of the excitation operator in terms of Goldstone matrix elements makes the resulting system of equations simple, compact and suitable for computer implementation. A pilot calculation has been performed to test the applicability of the theory.read more
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The equation-of-motion coupled-cluster method: Excitation energies of Be and CO
TL;DR: In this paper, an equation of motion coupled-cluster (EOM-CC) method for the calculation of excitation energies is presented, which is based upon representing an excited state as an excitation from a ground state and the excitation energy is obtained by solving a non-Hermitian eigenvalue problem.
Journal ArticleDOI
A linear response, coupled‐cluster theory for excitation energy
Hideo Sekino,Rodney J. Bartlett +1 more
TL;DR: In this paper, expressions for static and dynamic properties in coupled-cluster (CC) theory are derived using diagrammatic techniques and shown how consideration of orbital relaxation effects in the theory introduces higher-order correlation effects.
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Equation of motion coupled cluster method for electron attachment
TL;DR: The electron attachment equation of motion coupled cluster (EA•EOMCC) method is derived in this paper, which enables determination of the various bound states of an (N+1)-electron system and the corresponding energy eigenvalues relative to the energy of an N•electron CCSD reference state.
Journal ArticleDOI
On the connectivity criteria in the open-shell coupled-cluster theory for general model spaces
TL;DR: In this article, the authors study the open-shell coupled-cluster theories and examine the current theoretical status regarding the existence or non-existence of a linked-clusters theorem, ensuring the connectedness of the cluster amplitudes and the effective Hamiltonian.
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A critical assessment of coupled cluster method in quantum chemistry
Josef Paldus,Xiangzhu Li +1 more
References
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Journal ArticleDOI
Relationship between one-electron green's function and quantum chemical theories☆
Francis S.M. Tsui,Karl F. Freed +1 more
TL;DR: In this article, a one-electron Green's function theory is presented which is a close analog to sum-of-the-pairs type quantum chemical theories, and the approximate self-energy in this theory is expressed in terms of one and two electron energy-dependent functions describing the dynamical response of the correlated ground state to the removal and addition of an electron, respectively.
Journal ArticleDOI
Spin-adaptation in many-body perturbation theory
TL;DR: In this article, a spin-adapted Epstein-Nesbet (E-N) partition of the hamiltonian is defined, in which the diagonal matrix elements of the Hamiltonian in the Serber-type configurations figure as the unperturbed part.
Journal ArticleDOI
Resolvent operator approach to many‐body perturbation theory. III. Applications
TL;DR: The resolvent-based closed and open shell MBPT developed in the previous papers have been applied for the calculation of ionization potentials (I.P), electron afinities (E.A), excitation energies (E.), and correlation energies (C.E.) of several prototype atomic and molecular systems as mentioned in this paper.
Journal ArticleDOI
Resolvent operator approach to many‐body perturbation theory. I. Closed shells
TL;DR: In this paper, a time-dependent approach to many-body perturbation theory for closed shells based on the resolvent of the Schrodinger equation was developed, where φ and ψ are the unperturbed and exact wave functions for the system and E 0 is the correlation energy.
Journal ArticleDOI
Symmetry-adapted many-body perturbation theory: use of the wave operator matrix elements
TL;DR: In this article, the authors developed a simple method for adapting the closed-shell many-body perturbation theory to an arbitrary point group symmetry taking account of various classes of diagrams exactly to all orders.