The coupled cluster iteration scheme is analyzed as a multivariate discrete time map using nonlinear dynamics and synergetics. The nonlinearly coupled set of equations to determine the cluster amplitudes are driven by a fraction of the entire set of cluster amplitudes. These driver amplitudes enslave all other amplitudes through a synergistic inter-relationship, where the latter class of amplitudes behave as the auxiliary variables. The driver and the auxiliary variables exhibit vastly different time scales of relaxation during the iteration process to reach the fixed points. The fast varying auxiliary amplitudes are small in magnitude, while the driver amplitudes are large, and they have a much longer time scale of relaxation. Exploiting their difference in relaxation time scale, we employ an adiabatic decoupling approximation, where each of the fast relaxing auxiliary modes is expressed as a unique function of the principal amplitudes. This results in a tremendous reduction in the independent degrees of freedom. On the other hand, only the driver amplitudes are determined accurately via exact coupled cluster equations. We will demonstrate that the iteration scheme has an order of magnitude reduction in computational scaling than the conventional scheme. With a few pilot numerical examples, we would demonstrate that this scheme can achieve very high accuracy with significant savings in computational time.
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28 September 2021
Research Article|
September 29 2021
An approximate coupled cluster theory via nonlinear dynamics and synergetics: The adiabatic decoupling conditions
Valay Agarawal
;
Valay Agarawal
Department of Chemistry, Indian Institute of Technology Bombay
, Mumbai, India
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Chayan Patra
;
Chayan Patra
Department of Chemistry, Indian Institute of Technology Bombay
, Mumbai, India
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Rahul Maitra
Rahul Maitra
a)
Department of Chemistry, Indian Institute of Technology Bombay
, Mumbai, India
a)Author to whom correspondence should be addressed: [email protected]
Search for other works by this author on:
Valay Agarawal
Chayan Patra
Rahul Maitra
a)
Department of Chemistry, Indian Institute of Technology Bombay
, Mumbai, India
a)Author to whom correspondence should be addressed: [email protected]
J. Chem. Phys. 155, 124115 (2021)
Article history
Received:
June 15 2021
Accepted:
September 16 2021
Citation
Valay Agarawal, Chayan Patra, Rahul Maitra; An approximate coupled cluster theory via nonlinear dynamics and synergetics: The adiabatic decoupling conditions. J. Chem. Phys. 28 September 2021; 155 (12): 124115. https://doi.org/10.1063/5.0060087
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