Molecular orbital calculations on dinitrogen trioxide, N2O3

1977 ◽  
Vol 30 (12) ◽  
pp. 2613 ◽  
Author(s):  
IJ Doonan ◽  
RGAR Maclagan
Keyword(s):  
Molecular Orbital ◽  
Excited States ◽  
Molecular Orbital Calculation ◽  
Molecular Orbitals ◽  
Basis Set ◽  
Molecular Orbital Calculations ◽  
Localized Molecular Orbitals ◽  
Expansion Technique ◽  
Doubly Excited ◽  
Slater Basis

A minimal Slater basis set molecular orbital calculation on dinitrogen trioxide, N2O3, is reported. In the evaluation of integrals, non-NDDO integrals were calculated by the 3G/s expansion technique. Analysis of the wave function obtained shows weak bonding between the nitrosyl and nitro fragments and a very weak attractive interaction between the cis- oxygens. The molecular orbitals for N2O3 were expanded in terms of the NO and NO2 molecular orbitals. A correlation diagram linking the N2O3 orbitals with the NO and NO2 orbitals is presented. The localized molecular orbitals for N2O3 are analysed. A configuration interaction calculation involving the ground state and nine doubly excited state configurations is reported. Two excited states have significant contributions. A comparison is made between the results obtained by using a 3G/S expansion and a calculation using a 2G/S expansion.

scholarly journals Quantum Mechanics / Extremely Localized Molecular Orbital Embedding Strategy for Excited-States. 2. Coupling to the Equation-of-Motion Coupled Cluster Method

2020 ◽  
Author(s):  
Giovanni Macetti ◽  
Alessandro Genoni
Keyword(s):  
Quantum Mechanics ◽  
Molecular Orbital ◽  
Excited States ◽  
Quantum Chemical ◽  
Computational Cost ◽  
Equation Of Motion ◽  
Molecular Orbitals ◽  
Cluster Method ◽  
Coupled Cluster ◽  
Localized Molecular Orbitals

Equation-of-Motion Coupled Cluster with single and double excitations (EOM-CCSD) is currently one of the most accurate quantum chemical methods for the investigation of excited-states, but its non-negligible computational cost unfortunately limits its application to small molecules. To extend its range of applicability, one possibility consists in its coupling with the so-called multi-scale embedding techniques. Along this line, in this work we propose the interface of the EOM-CCSD method with the recently developed quantum mechanics / extremely localized molecular orbital (QM/ELMO) strategy, an approach where the chemically relevant region of the investigated system is treated at fully quantum chemical level (QM region), while the remaining part (namely, the chemical environment) is described through transferred and frozen extremely localized molecular orbitals (ELMO subsystem). In order to determine capabilities and limitations of the novel EOM-CCSD/ELMO approach, some validation tests were properly designed and carried out. They indicated that the new approach is particularly useful and efficient in describing local electronic transitions in relatively large systems, for both covalently and non-covalently bonded QM and ELMO regions. In particular, it has been shown that, including only a limited number of atoms in the chemically active subunit, the ELMO-embedded computations enable the reproduction of excitation energies and oscillator strengths resulting from full EOM-CCSD calculations within the limit of chemical accuracy, but with a significantly reduced computational cost. Furthermore, despite the approximation of an embedding potential given by frozen extremely localized molecular orbitals, it was observed that the new strategy is able to satisfactorily account for the effects of the environment.

scholarly journals Quantum Mechanics / Extremely Localized Molecular Orbital Embedding Strategy for Excited-States. 2. Coupling to the Equation-of-Motion Coupled Cluster Method

2020 ◽  
Author(s):  
Giovanni Macetti ◽  
Alessandro Genoni
Keyword(s):  
Quantum Mechanics ◽  
Molecular Orbital ◽  
Excited States ◽  
Quantum Chemical ◽  
Computational Cost ◽  
Equation Of Motion ◽  
Molecular Orbitals ◽  
Cluster Method ◽  
Coupled Cluster ◽  
Localized Molecular Orbitals

Equation-of-Motion Coupled Cluster with single and double excitations (EOM-CCSD) is currently one of the most accurate quantum chemical methods for the investigation of excited-states, but its non-negligible computational cost unfortunately limits its application to small molecules. To extend its range of applicability, one possibility consists in its coupling with the so-called multi-scale embedding techniques. Along this line, in this work we propose the interface of the EOM-CCSD method with the recently developed quantum mechanics / extremely localized molecular orbital (QM/ELMO) strategy, an approach where the chemically relevant region of the investigated system is treated at fully quantum chemical level (QM region), while the remaining part (namely, the chemical environment) is described through transferred and frozen extremely localized molecular orbitals (ELMO subsystem). In order to determine capabilities and limitations of the novel EOM-CCSD/ELMO approach, some validation tests were properly designed and carried out. They indicated that the new approach is particularly useful and efficient in describing local electronic transitions in relatively large systems, for both covalently and non-covalently bonded QM and ELMO regions. In particular, it has been shown that, including only a limited number of atoms in the chemically active subunit, the ELMO-embedded computations enable the reproduction of excitation energies and oscillator strengths resulting from full EOM-CCSD calculations within the limit of chemical accuracy, but with a significantly reduced computational cost. Furthermore, despite the approximation of an embedding potential given by frozen extremely localized molecular orbitals, it was observed that the new strategy is able to satisfactorily account for the effects of the environment.

Molecular orbital calculation of biomolecules with fragment molecular orbitals

2009 ◽  
Vol 476 (1-3) ◽  
pp. 104-108 ◽  
Author(s):  
Shinji Tsuneyuki ◽  
Tomoki Kobori ◽  
Kazuto Akagi ◽  
Keitaro Sodeyama ◽  
Kiyoyuki Terakura ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
Molecular Orbital Calculation ◽  
Molecular Orbitals

Ab Initio SCF Procedure with Localized Molecular Orbitals of Fragments

1975 ◽  
Vol 30 (11) ◽  
pp. 1499
Author(s):  
J. Koller ◽  
A. Ažman
Keyword(s):  
Ab Initio ◽  
Molecular Orbitals ◽  
Basis Set ◽  
Localized Orbitals ◽  
Localized Molecular Orbitals ◽  
Molecular Systems

An ab initio procedure is described with a basis set of localized orbitals of the fragments. The method was tested on three molecular systems. The results are in agreement with the results of LCAO calculations

Inductive Effects on Molecular Ionization Potentials, XVIII Alkylpyridines and Alkylthiophenes. Molecular Orbital Calculations on Alkylbenzenes and Alkylpyridines

1977 ◽  
Vol 32 (10) ◽  
pp. 1160-1164 ◽  
Author(s):  
Cyril Párkányi ◽  
Leonard S. Levitt
Keyword(s):  
Molecular Orbital ◽  
Linear Correlation ◽  
Molecular Orbitals ◽  
Ionization Potentials ◽  
Molecular Orbital Calculations ◽  
Alkyl Groups ◽  
Inductive Effects ◽  
Substituent Constants ◽  
Linear Correlations ◽  
Molecular Ionization

Models of alkylbenzenes were treated by the HMO and SCF—MO methods and excellent linear correlations were found between the experimental ionization potentials, EI, and the energies of the highest occupied π-molecular orbitals calculated by the above-mentioned methods. A similar linear correlation was obtained for a group of methylpyridines. Also, the experimental ionization potentials of methylpyridines and alkylthiophenes have been linearly correlated with the sum of TAFT'S inductive substituent constants, ΣσI of the alkyl groups.

Molecular Orbital Calculations of Excited States of H2

1962 ◽  
Vol 36 (8) ◽  
pp. 2140-2144 ◽  
Author(s):  
Joseph T. Zung ◽  
A. B. F. Duncan
Keyword(s):  
Molecular Orbital ◽  
Excited States ◽  
Molecular Orbital Calculations

Ab initio molecular orbital calculations of the ground and excited states of the permanganate and chromate ions

1970 ◽  
Vol 320 (1541) ◽  
pp. 161-173 ◽  
Keyword(s):  
Molecular Orbital ◽  
Excited States ◽  
Slater Type Orbitals ◽  
Molecular Orbital Calculations ◽  
Field Equations ◽  
Chromate Ions ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
State Wavefunctions

The bonding in the permanganate and chromate ions is described by means of self-consistent field molecular orbital calculations employing a basis of Slater type orbitals expanded in Gaussian type functions. A new procedure for the solution of the self-consistent field equations is described and applied to the ions studied here. Excited state wavefunctions are calculated using configuration interaction considering all singly excited configurations involving all virtual and valence orbitals. The calculated transition energies and transition moments are compared with those from the experimental electronic spectra.

Protonation Effect on C-N Bond Length of Alkylamines Studied by Molecular Orbital Calculations

2000 ◽  
Vol 55 (9-10) ◽  
pp. 769-771 ◽  
Keyword(s):  
Density Functional Theory ◽  
Bond Length ◽  
Molecular Orbital ◽  
Density Functional ◽  
Second Order ◽  
Basis Set ◽  
Molecular Orbital Calculations ◽  
Functional Theory ◽  
Hartree Fock ◽  
Protonation Effect

Abstract Molecular orbital calculations were performed for the six saturated alkylamines (CH3NH2 , (CH3)2 NH, (CH 3)3 N, CH 3CH2NH2 , (CH3)2 CHNH2 , (CH3)3 CNH2), their protonated cations (CH3NH3 + , (CH3)2NH2 + , (CH3)3NH + , CH3CH2NH3 + , (CH3)2CHNH3 + , (CH3)3CNH3+), and (CH3)4 N + using the Hartree-Fock, second-order M0ller-Plesset, and density functional theory methods with the 6-311+G(d,p) basis set. Protonation lengthens the C-N bonds of the amines by 0.05 -0.08 Å and shortens the C-C bonds of CH3CH2NH2, (CH3)2CHNH2 , and (CH3)3CNH2 by ca. 0.01 Å.

Sign in / Sign up

Export Citation Format

Share Document