Theoretical study of singlet-triplet and triplet-triplet spectra. I. Selection of parameters and the basis of configuration interaction in closed shell and restricted open shell semiempirical methods

1973 ◽  
Vol 77 (1) ◽  
pp. 107-113 ◽  
Author(s):  
J. Pancir ◽  
R. Zahradnik
Keyword(s):  
Configuration Interaction ◽  
Theoretical Study ◽  
Closed Shell ◽  
Open Shell ◽  
Semiempirical Methods ◽  
Selection Of

THEORETICAL STUDY ON THE SECOND HYPERPOLARIZABILITY (γ) OF A HOMOGENEOUS MOLECULE IN THE BOND DISSOCIATION PROCESS: ENHANCEMENT OF γ IN THE INTERMEDIATE CORRELATION REGIME

2004 ◽  
Vol 13 (03n04) ◽  
pp. 411-416 ◽  
Author(s):  
MASAYOSHI NAKANO ◽  
SATORU YAMADA ◽  
RYOHEI KISHI ◽  
MASAHIRO TAKAHATA ◽  
TOMOSHIGE NITTA ◽  
...  
Keyword(s):  
Finite Field ◽  
Density Functional ◽  
Theoretical Study ◽  
Closed Shell ◽  
Open Shell ◽  
Neutral Systems ◽  
Dissociation Process ◽  
Second Hyperpolarizability ◽  
Bond Dissociation ◽  
Neutral Compounds

The variation in the longitudinal second hyperpolarizability (γ) in the bond-dissociation process of a homogeneous molecule ( H 2) is investigated by the finite-field (FF) approach using several ab initio molecular orbital (MO) and density functional (DF) methods. The most accurate methods (UCCSD or RCCSD) employed in this study show that the magnitude of γ value is remarkably enhanced in the intermediate dissociation region, which corresponds to the intermediate correlation regime. Such behavior suggests that the magnitudes of γ values for open-shell neutral compounds in the intermediate correlation regime are remarkably enhanced as compared to the usual closed-shell neutral systems.

scholarly journals Generalized Single Excitation Configuration Interaction: An Investigation into the Impact of the Inclusion of Non-Orthogonality on the Calculation of Core-Excited States

2019 ◽  
Author(s):  
Katherine J. Oosterbaan ◽  
Alec F. White ◽  
Diptarka Hait ◽  
Martin Head-Gordon
Keyword(s):  
Excited States ◽  
Configuration Interaction ◽  
Ground States ◽  
Closed Shell ◽  
Open Shell ◽  
Spatial Symmetry ◽  
Exchange Approximation ◽  
Novel Method ◽  
The Impact

<div>In this paper, we investigate different non-orthogonal generalizations of the configuration interaction with single substitutions (CIS) method for the calculation of core-excited states. Fully non-orthogonal CIS (NOCIS) has been described previously for singlets and doublets and this paper reports the extension to triplet molecules. In addition to NOCIS, we present a novel method, 1C-NOCIS(1C-NOCIS), for open-shell molecules which is intermediate between NOCIS and the static exchange approximation (STEX). We explore this hierarchy of spin-pure methods for singlet, doublet, and triplet molecules and conclude that, while NOCIS provides the best results and preserves the spatial symmetry of the wavefunction, 1C-NOCIS retains much of the accuracy of NOCIS at a dramatically reduced cost. For molecules with closed-shell ground states, STEX and 1C-NOCIS are identical.</div>

scholarly journals Generalized Single Excitation Configuration Interaction: An Investigation into the Impact of the Inclusion of Non-Orthogonality on the Calculation of Core-Excited States

2019 ◽  
Author(s):  
Katherine J. Oosterbaan ◽  
Alec F. White ◽  
Diptarka Hait ◽  
Martin Head-Gordon
Keyword(s):  
Excited States ◽  
Configuration Interaction ◽  
Ground States ◽  
Closed Shell ◽  
Open Shell ◽  
Spatial Symmetry ◽  
Exchange Approximation ◽  
Novel Method ◽  
The Impact

<div>In this paper, we investigate different non-orthogonal generalizations of the configuration interaction with single substitutions (CIS) method for the calculation of core-excited states. Fully non-orthogonal CIS (NOCIS) has been described previously for singlets and doublets and this paper reports the extension to triplet molecules. In addition to NOCIS, we present a novel method, 1C-NOCIS(1C-NOCIS), for open-shell molecules which is intermediate between NOCIS and the static exchange approximation (STEX). We explore this hierarchy of spin-pure methods for singlet, doublet, and triplet molecules and conclude that, while NOCIS provides the best results and preserves the spatial symmetry of the wavefunction, 1C-NOCIS retains much of the accuracy of NOCIS at a dramatically reduced cost. For molecules with closed-shell ground states, STEX and 1C-NOCIS are identical.</div>

Transalkylierung und protonenkatalysierte C-C-Spaltung bei n-Butyl-und n-Pentylbenzol in der Gasphase / Transalkylation and Proton Catalyzed C-C-Cleavage of Gaseous n-Butyl and w-Pentyl Benzenes

1979 ◽  
Vol 34 (3) ◽  
pp. 495-501 ◽  
Author(s):  
C. Wesdemiotis ◽  
H. Schwarz ◽  
C. C. Van de Sande ◽  
F. Van Gaever
Keyword(s):  
Hydrogen Exchange ◽  
Closed Shell ◽  
Open Shell ◽  
Molecular Ions ◽  
Exchange Reactions ◽  
Intramolecular Exchange ◽  
Carbon Carbon Bond ◽  
Exchange Processes ◽  
Reaction Channels ◽  
Alkyl Benzenes

Abstract The investigation of several 13carbon and deuterium labelled n-butyl and n-pentyl benzenes demonstrate that chemical ionization (reagent gas: methane) induces specific carbon-carbon bond cleavages of the alkyl group. The extent of competing reaction channels as for instance direct alkene elimination versus dealkylation/reprotonation is analyzed. Partial hydrogen exchange processes between reagent ions and substrate molecules are restricted to the phenyl ring. Intramolecular exchange reactions between the side chain and the aromatic ring which are typical for the open shell molecular ions of alkyl benzenes are not observed for analogous closed shell cations.

scholarly journals Exploring Cu/Al cluster growth and reactivity: from embryonic building blocks to intermetalloid, open-shell superatoms

2021 ◽  
Author(s):  
Max Schütz ◽  
Christian Gemel ◽  
Maximilian Muhr ◽  
Christian Jandl ◽  
Samia Kahlal ◽  
...  
Keyword(s):  
Closed Shell ◽  
Building Blocks ◽  
Open Shell ◽  
Cluster Growth ◽  
Powerful Technique

Cu/Al cluster growth reactions leading to open- and closed-shell superatoms are investigated. Therein, LIFDI-MS is presented as a powerful technique for the in situ detection of cluster identities and reactivity patterns.

The Way of Obtain C3H4O+ Fragments Laser-Induced by Cycloheptanone Ion Excited State

2014 ◽  
Vol 887-888 ◽  
pp. 931-934
Author(s):  
Hong Bin Chen ◽  
Ying Zhu ◽  
Jie Wu
Keyword(s):  
Excited State ◽  
Configuration Interaction ◽  
Theoretical Study ◽  
Vibrational Frequencies ◽  
State Structure ◽  
The Way

Our theoretical study aims to the way of obtain C3H4O+ fragments laser-induced by Cycloheptanone ion (C7H12O+ ) excited state and gives out a result with proved and directed significance for the corresponding experiments. Using the CIS（Configuration Interaction with Single Substitute） method, calculated Cycloheptanone ion excited state structure and vibrational frequencies.

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