scholarly journals Communication: Configuration interaction combined with spin-projection for strongly correlated molecular electronic structures

2016 ◽  
Vol 144 (1) ◽  
pp. 011101 ◽  
Author(s):  
Takashi Tsuchimochi ◽  
Seiichiro Ten-no
Keyword(s):  
Configuration Interaction ◽  
Electronic Structures ◽  
Spin Projection ◽  
Strongly Correlated ◽  
Molecular Electronic

scholarly journals Low-Cost Molecular Excited States from a State-Averaged Resonating Hartree-Fock Approach

2019 ◽  
Author(s):  
Jacob Nite ◽  
Carlos A. Jimenez-Hoyos
Keyword(s):  
Excited States ◽  
Configuration Interaction ◽  
Low Cost ◽  
Computational Cost ◽  
Mean Field ◽  
Chem Phys ◽  
Spin Projection ◽  
Excitation Energies ◽  
Hartree Fock ◽  
Orbital Relaxation

Quantum chemistry methods that describe excited states on the same footing as the ground state are generally scarce. In previous work, Gill et al. (J. Phys. Chem. A 112, 13164 (2008)) and later Sundstrom and Head-Gordon (J. Chem. Phys. 140, 114103 (2014)) considered excited states resulting from a non-orthogonal configuration interaction (NOCI) on stationary solutions of the Hartree–Fock equations. We build upon those contributions and present the state-averaged resonating Hartree–Fock (sa-ResHF) method, which differs from NOCI in that spin-projection and orbital relaxation effects are incorporated from the onset. Our results in a set of small molecules (alanine, formaldehyde, acetaldehyde, acetone, formamide, and ethylene) suggest that sa-ResHF excitation energies are a notable improvement over configuration interaction singles (CIS), at a mean-field computational cost. The orbital relaxation in sa-ResHF, in the presence of a spin-projection operator, generally results in excitation energies that are closer to the experimental values than the corresponding NOCI ones.

scholarly journals Low-Cost Molecular Excited States from a State-Averaged Resonating Hartree-Fock Approach

2019 ◽  
Author(s):  
Jacob Nite ◽  
Carlos A. Jimenez-Hoyos
Keyword(s):  
Excited States ◽  
Configuration Interaction ◽  
Low Cost ◽  
Computational Cost ◽  
Mean Field ◽  
Chem Phys ◽  
Spin Projection ◽  
Excitation Energies ◽  
Hartree Fock ◽  
Orbital Relaxation

Quantum chemistry methods that describe excited states on the same footing as the ground state are generally scarce. In previous work, Gill et al. (J. Phys. Chem. A 112, 13164 (2008)) and later Sundstrom and Head-Gordon (J. Chem. Phys. 140, 114103 (2014)) considered excited states resulting from a non-orthogonal configuration interaction (NOCI) on stationary solutions of the Hartree–Fock equations. We build upon those contributions and present the state-averaged resonating Hartree–Fock (sa-ResHF) method, which differs from NOCI in that spin-projection and orbital relaxation effects are incorporated from the onset. Our results in a set of small molecules (alanine, formaldehyde, acetaldehyde, acetone, formamide, and ethylene) suggest that sa-ResHF excitation energies are a notable improvement over configuration interaction singles (CIS), at a mean-field computational cost. The orbital relaxation in sa-ResHF, in the presence of a spin-projection operator, generally results in excitation energies that are closer to the experimental values than the corresponding NOCI ones.

Supramolecular structures of N 4-substituted 2,4-diamino-6-benzyloxy-5-nitrosopyrimidines

2003 ◽  
Vol 59 (2) ◽  
pp. 263-276 ◽  
Author(s):  
Manuel Melguizo ◽  
Antonio Quesada ◽  
John N. Low ◽  
Christopher Glidewell
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Intermolecular Interactions ◽  
Electronic Structures ◽  
Supramolecular Structure ◽  
Supramolecular Structures ◽  
Stacking Interactions ◽  
Molecular Electronic ◽  
Π Stacking

The molecular and supramolecular structures of eight N 4-substituted 2,4-diamino-6-benzyloxy-5-nitrosopyrimidines are discussed, along with one analogue containing no nitroso substituent. The nitroso derivatives all exhibit polarized molecular-electronic structures leading to extensive charge-assisted hydrogen bonding between the molecules. The intermolecular interactions include hard hydrogen bonds of N—H...O and N—H...N types, together with O—H...O and O—H...N types in the monohydrate of 2-amino-6-benzyloxy-4-piperidino-5-nitrosopyrimidine, soft hydrogen bonds of C—H...O, C—H...π(arene) and N—H...π(arene) types and aromatic π...π stacking interactions. The predominant supramolecular structure types take the form of chains and sheets, but no two of the structures determined here exhibit the same combination of hydrogen-bond types.

Spin–flip non-orthogonal configuration interaction: a variational and almost black-box method for describing strongly correlated molecules

2014 ◽  
Vol 16 (41) ◽  
pp. 22694-22705 ◽  
Author(s):  
Nicholas J. Mayhall ◽  
Paul R. Horn ◽  
Eric J. Sundstrom ◽  
Martin Head-Gordon
Keyword(s):  
Configuration Interaction ◽  
Black Box ◽  
Strongly Correlated ◽  
Spin Flip ◽  
Box Method

scholarly journals Basis Set Dependency of Molecular Electronic Structures

1986 ◽  
Vol 59 (9) ◽  
pp. 2729-2733 ◽  
Author(s):  
Hiroshi Ichikawa ◽  
Keiichiro Sameshima ◽  
Yukiko Ebisawa
Keyword(s):  
Electronic Structures ◽  
Basis Set ◽  
Molecular Electronic
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