scholarly journals Unitary coupled-cluster based self-consistent polarization propagator theory: A quadratic unitary coupled-cluster singles and doubles scheme

2021 ◽  
Vol 155 (17) ◽  
pp. 174102
Author(s):  
Junzi Liu ◽  
Lan Cheng
Keyword(s):  
Coupled Cluster ◽  
Polarization Propagator ◽  
Self Consistent ◽  
Propagator Theory

A self-consistent quasidegenerate coupled-cluster theory

1999 ◽  
Vol 311 (5) ◽  
pp. 372-378 ◽  
Author(s):  
Mark R. Hoffmann ◽  
Yuriy G. Khait
Keyword(s):  
Coupled Cluster ◽  
Coupled Cluster Theory ◽  
Cluster Theory ◽  
Self Consistent

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.

Polarization propagator theory and the entanglement between MO excitations

2018 ◽  
Vol 20 (38) ◽  
pp. 24832-24842 ◽  
Author(s):  
Leonardo A. Millán ◽  
Claudia G. Giribet ◽  
Gustavo A. Aucar
Keyword(s):  
Quantum Entanglement ◽  
Molecular Systems ◽  
Polarization Propagator ◽  
External Perturbations ◽  
Propagator Theory ◽  
The Way

The likely quantum entanglement among excitations of MOs is described by using the polarization propagator formalism. Its first application to NMR-J couplings gives new understanding about the way external perturbations are transmitted within molecular systems.

On the dissociation energy of Ti(OH2)+. An MCSCF, CCSD(T), and DFT study

1996 ◽  
Vol 74 (10) ◽  
pp. 1824-1829 ◽  
Author(s):  
A. Irigoras ◽  
J.M. Ugalde ◽  
X. Lopez ◽  
C. Sarasola
Keyword(s):  
Dissociation Energy ◽  
Density Functional ◽  
Basis Sets ◽  
Coupled Cluster ◽  
Functional Theory ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Self Consistent Field Theory ◽  
Effective Core Potentials

The dissociation energy of the Ti(OH2)+ ion–molecule complex was calculated by the multiconfigurational self-consistent field theory, coupled cluster theory, and two density functional theory based methods, using both all-electron basis sets and effective core potentials. The calculations show that approximate density functional theory gives results in better agreement with experiment than either the multiconfigurational self-consistent field theory or the coupled cluster theory, with both all-electron basis sets and effective core potentials. Nevertheless, the optimized geometries and harmonic vibration frequencies are very similar, irrespective of the level of theory used. The interconfigurational energy ordering of the two valence electronic configurations dn−1s and dn−2s2 of the 4F electronic state of the titanium cation were also calculated and are discussed. Key words: ab initio, dissociation energy, ion–molecule complex, effective core potentials, transition metals.

A Comparison of Møller-Plesset and Coupled Cluster Linear Response Theory Methods for the Calculation of Dipole Oscillator Strength Sum Rules and C6 Dispersion Coefficients

2008 ◽  
Vol 73 (11) ◽  
pp. 1415-1436 ◽  
Author(s):  
Ivana Paidarová ◽  
Stephan P. A. Sauer
Keyword(s):  
Oscillator Strength ◽  
Linear Response ◽  
Sum Rules ◽  
Linear Response Theory ◽  
Second Order ◽  
Coupled Cluster ◽  
Response Theory ◽  
Polarization Propagator ◽  
Dipole Oscillator ◽  
Moller Plesset

Four correlated linear response theory methods - the second order polarization propagator approximation (SOPPA), the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes, SOPPA(CCSD), the CC2 and coupled cluster singles doubles (CCSD) linear response theory - were used to determine the dipole oscillator strength sum rules of the hydrogen halides HX (with X = F, Cl, Br and I) and the C6 dispersion coefficient for all pairs of interacting HX molecules via numerical integration of the Casimir-Polder formula. The dependence of the polarizabilities, their frequency dependence and the C6 coefficients on the level of correlation and the dependence of the C6 coefficients on the two intramolecular bond lengths were studied.

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