Multireference Coupled-Cluster Approach to Spectroscopic Constants: Molecular Geometries and Harmonic Frequencies

1992 ◽  
pp. 213-231 ◽  
Author(s):  
Uzi Kaldor
Keyword(s):  
Spectroscopic Constants ◽  
Coupled Cluster ◽  
Cluster Approach ◽  
Harmonic Frequencies

scholarly journals Theoretical Electronic and Rovibrational Studies for Anions of Interest to the DIBs

2013 ◽  
Vol 9 (S297) ◽  
pp. 344-348 ◽  
Author(s):  
R. C. Fortenberry
Keyword(s):  
Excited State ◽  
Excited States ◽  
State Of The Art ◽  
Spectroscopic Constants ◽  
Coupled Cluster ◽  
Electronic Excitations ◽  
Electronically Excited States ◽  
Coupled Cluster Theory ◽  
Electronically Excited ◽  
Enolate Anion

AbstractThe dipole-bound excited state of the methylene nitrile anion (CH2CN−) has been suggested as a candidate carrier for a diffuse interstellar band (DIB) at 803.8 nm. Its corresponding radical has been detected in the interstellar medium (ISM), making the existence for the anion possible. This work applies state-of-the-art ab initio methods such as coupled cluster theory to reproduce accurately the electronic excitations for CH2CN− and the similar methylene enolate anion, CH2CHO−. This same approach has been employed to indicate that 19 other anions may possess electronically excited states, five of which are valence in nature. Concurrently, in order to assist in the detection of these anions in the ISM, work has also been directed towards predicting vibrational frequencies and spectroscopic constants for these anions through the use of quartic force fields (QFFs). Theoretical rovibrational work on anions has thus far included studies of CH2CN−, C3H−, and is currently ongoing for similar systems.

Valence bond corrected single reference coupled cluster approach

1994 ◽  
Vol 89 (1) ◽  
pp. 33-57 ◽  
Author(s):  
J. Planelles ◽  
J. Paldus ◽  
X. Li
Keyword(s):  
Valence Bond ◽  
Coupled Cluster ◽  
Cluster Approach

A coupled-cluster approach to the relative strains in [1.1.1]propellane, its derivatives and hetero[1.1.1]propellanes

2012 ◽  
Vol 110 (19-20) ◽  
pp. 2349-2357 ◽  
Author(s):  
Hanying Xu ◽  
Svein Saebo ◽  
Charles U. Pittman
Keyword(s):  
Coupled Cluster ◽  
Cluster Approach

An orbital-invariant internally contracted multireference coupled cluster approach

2011 ◽  
Vol 134 (11) ◽  
pp. 114102 ◽  
Author(s):  
Francesco A. Evangelista ◽  
Jürgen Gauss
Keyword(s):  
Coupled Cluster ◽  
Cluster Approach

Time-Independent Coupled-Cluster Theory of the Polarization Propagator

2005 ◽  
Vol 70 (8) ◽  
pp. 1109-1132 ◽  
Author(s):  
Robert Moszynski ◽  
Piotr S. Żuchowski ◽  
Bogumił Jeziorski
Keyword(s):  
Order Term ◽  
Cluster Method ◽  
Coupled Cluster ◽  
Cluster Approach ◽  
Coupled Cluster Theory ◽  
Cluster Theory ◽  
Polarization Propagator ◽  
Apparent Correlation ◽  
Moller Plesset ◽  
New Formulation

A novel, time-independent formulation of the coupled-cluster theory of the polarization propagator is presented. This formulation, unlike the equation-of-motion coupled-cluster approach, is fully size-extensive and, unlike the conventional time-dependent coupled-cluster method, is manifestly Hermitian, which guarantees that the polarization propagator is always real for purely imaginary frequencies and that the resulting polarizabilities exhibit time-reversal symmetry (are even functions of frequency) for purely real or purely imaginary perturbations. This new formulation is used to derive compact expressions for the three leading terms in the Møller-Plesset expansion for the polarization propagator. The true and apparent correlation contributions to the second-order term are analyzed and separated at the operator level. Explicit equations for the polarization propagator at the non-perturbative, singles and doubles level (CCSD) are presented.

scholarly journals Reply to comment on: Coupled cluster approach or quadratic configuration interaction?

1990 ◽  
Vol 93 (2) ◽  
pp. 1486-1487 ◽  
Author(s):  
Krishnan Raghavachari ◽  
Martin Head‐Gordon ◽  
John A. Pople
Keyword(s):  
Configuration Interaction ◽  
Coupled Cluster ◽  
Cluster Approach
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