scholarly journals Exploration of interlacing and avoided crossings in a manifold of potential energy curves by a unitary group adapted state specific multi-reference perturbation theory (UGA-SSMRPT)

2021 ◽  
Vol 155 (1) ◽  
pp. 014101
Author(s):  
Dibyajyoti Chakravarti ◽  
Koustav Hazra ◽  
Riya Kayal ◽  
Sudip Sasmal ◽  
Debashis Mukherjee
Keyword(s):  
Perturbation Theory ◽  
Potential Energy ◽  
Unitary Group ◽  
Potential Energy Curves ◽  
Avoided Crossings

Second-order generalized Van Vleck perturbation theory calculations of potential energy curves for the dissociation of the C–H bond in methane

2007 ◽  
Vol 105 (19-22) ◽  
pp. 2819-2827 ◽  
Author(s):  
Alexander Azenkeng ◽  
Yuriy G. Khait ◽  
Mark R. Hoffmann
Keyword(s):  
Perturbation Theory ◽  
Potential Energy ◽  
Second Order ◽  
Potential Energy Curves ◽  
Van Vleck

scholarly journals Diabatic potential energy curves for the $$^4{\Pi} $$ states of SH

2021 ◽  
Vol 140 (6) ◽  
Author(s):  
D. O. Kashinski ◽  
J. Bohnemann ◽  
A. P. Hickman ◽  
D. Talbi
Keyword(s):  
Potential Energy ◽  
High Accuracy ◽  
Potential Energy Curves ◽  
Hamiltonian Matrix ◽  
Block Diagonalization ◽  
Diagonalization Method ◽  
Avoided Crossings ◽  
Diabatic Representation ◽  
Nuclear Geometry ◽  
Valence Mixing

AbstractWe present a diabatic representation of the potential energy curves (PECs) for the $$^4{{\Pi}} $$ 4 Π states of $$\mathrm {SH}$$ SH . Multireference, configuration interaction (MRCI) calculations were used to determine high-accuracy adiabatic PECs of both $$\mathrm {SH}$$ SH and $${\mathrm {SH}}^+$$ SH + from which the diabatic representation is constructed for $$\mathrm {SH}$$ SH . The adiabatic PECs exhibit many avoided crossings due to strong Rydberg-valence mixing. We employ the block diagonalization method, an orthonormal rotation of the adiabatic Hamiltonian, to disentangle the valence autoionizing and Rydberg $$^4\Pi $$ 4 Π states of $$\mathrm {SH}$$ SH by constructing a diabatic Hamiltonian. The diagonal elements of the diabatic Hamiltonian matrix at each nuclear geometry render the diabatic PECs and the off-diagonal elements are related to the state-to-state coupling. Care is taken to assure smooth variation and consistency of chemically significant molecular orbitals across the entire geometry domain.

Resonant x-ray Raman Scattering involving avoided crossings in the final-state potential-energy curves

2000 ◽  
Vol 62 (6) ◽  
Author(s):  
P. Sałek ◽  
R. Fink ◽  
F. Gel’mukhanov ◽  
M. Piancastelli ◽  
R. Feifer ◽  
...  
Keyword(s):  
Potential Energy ◽  
Raman Scattering ◽  
Potential Energy Curves ◽  
Final State ◽  
X Ray ◽  
State Potential ◽  
Avoided Crossings

scholarly journals Capturing Static and Dynamic Correlation with ΔNO-MP2 and ΔNO-CCSD

2019 ◽  
Author(s):  
joshua wallace hollett ◽  
Pierre-Francois Loos
Keyword(s):  
Perturbation Theory ◽  
Potential Energy ◽  
Second Order ◽  
Potential Energy Curves ◽  
Coupled Cluster ◽  
Dynamic Correlation ◽  
Static Correlation ◽  
Selection Of ◽  
Plesset Perturbation Theory ◽  
Good Agreement

<p>The NO method for static correlation is combined with second-order Mller-Plesset perturbation theory (MP2) and coupled-cluster singles and doubles (CCSD) to account for dynamic correlation. The MP2 and CCSD expressions are adapted from nite-temperature CCSD, which includes orbital occupancies and vacancies, and expanded orbital summations. Correlation is partitioned with the aid of damping factors incorporated into the MP2 and CCSD residual equations. Potential energy curves for a selection of diatomics are in good agreement with extrapolated full conguration interaction results (exFCI), and on par with conventional multireference approaches.<br></p>

Detection of spurious avoided crossings of potential energy curves

1979 ◽  
Vol 70 (6) ◽  
pp. 2958-2961 ◽  
Author(s):  
Tucker Carrington
Keyword(s):  
Potential Energy ◽  
Potential Energy Curves ◽  
Avoided Crossings

scholarly journals Capturing Static and Dynamic Correlation with ΔNO-MP2 and ΔNO-CCSD

2019 ◽  
Author(s):  
joshua wallace hollett ◽  
Pierre-Francois Loos
Keyword(s):  
Perturbation Theory ◽  
Potential Energy ◽  
Second Order ◽  
Potential Energy Curves ◽  
Coupled Cluster ◽  
Dynamic Correlation ◽  
Static Correlation ◽  
Selection Of ◽  
Plesset Perturbation Theory ◽  
Good Agreement

<p>The NO method for static correlation is combined with second-order Mller-Plesset perturbation theory (MP2) and coupled-cluster singles and doubles (CCSD) to account for dynamic correlation. The MP2 and CCSD expressions are adapted from nite-temperature CCSD, which includes orbital occupancies and vacancies, and expanded orbital summations. Correlation is partitioned with the aid of damping factors incorporated into the MP2 and CCSD residual equations. Potential energy curves for a selection of diatomics are in good agreement with extrapolated full conguration interaction results (exFCI), and on par with conventional multireference approaches.<br></p>

Applications of perturbation theory to the chemical problems potential energy curves of BH, F2and N2

1979 ◽  
Vol 38 (5) ◽  
pp. 1621-1633 ◽  
Author(s):  
Miroslav Urban ◽  
Vladimír Kellö
Keyword(s):  
Perturbation Theory ◽  
Potential Energy ◽  
Potential Energy Curves
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