The Second-Order-Polarization-Propagator-Approximation (SOPPA) in a four-component spinor basis

A theoretical framework for understanding molecular structures is crucial for the development of new technologies such as catalysts or solar cells. Apart from electronic excitation energies, however, only spectroscopic properties of molecules consisting of lighter elements can be computationally des...

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Bibliographic Details
Published in:The Journal of chemical physics 2020-04, Vol.152 (13), p.134113-134113
Main Authors: Schnack-Petersen, Anna Kristina, Simmermacher, Mats, Fasshauer, Elke, Jensen, Hans Jørgen Aa, Sauer, Stephan P. A.
Format: Article
Language:English
Subjects:
Approximation
Charged particles
Excitation
Heavy elements
Mathematical analysis
Molecular structure
New technology
Photovoltaic cells
Physics
Polarization
Quantum chemistry
Relativistic effects
Solar cells
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Summary:A theoretical framework for understanding molecular structures is crucial for the development of new technologies such as catalysts or solar cells. Apart from electronic excitation energies, however, only spectroscopic properties of molecules consisting of lighter elements can be computationally described at a high level of theory today since heavy elements require a relativistic framework, and thus far, most methods have only been derived in a non-relativistic framework. Important new technologies such as those mentioned above require molecules that contain heavier elements, and hence, there is a great need for the development of relativistic computational methods at a higher level of accuracy. Here, the Second-Order-Polarization-Propagator-Approximation (SOPPA), which has proven to be very successful in the non-relativistic case, is adapted to a relativistic framework. The equations for SOPPA are presented in their most general form, i.e., in a non-canonical spin–orbital basis, which can be reduced to the canonical case, and the expressions needed for a relativistic four-component SOPPA are obtained. The equations are one-index transformed, giving more compact expressions that correspond to those already available for the four-component RPA. The equations are ready for implementation in a four-component quantum chemistry program, which will allow both linear response properties and excitation energies to be calculated relativistically at the SOPPA level.
ISSN:0021-9606
1089-7690
DOI:10.1063/5.0002389