Optimization of selected molecular orbitals in group basis sets

2009 ◽  
Vol 130 (13) ◽  
pp. 134108 ◽  
Author(s):  
György G. Ferenczy ◽  
William H. Adams
Keyword(s):  
Molecular Orbitals ◽  
Basis Sets ◽  
Group Basis

scholarly journals Structure, Vibrations, Molecular Orbitals, Reactivity Properties of 3-Trifluoromethylphenylchloroformate by FT-IR, FT-Raman, FT-NMR and DFT Studies

2019 ◽  
Vol 31 (8) ◽  
pp. 1737-1747
Author(s):  
V. Arjunan ◽  
S. Senthilkumari ◽  
S. Mohan
Keyword(s):  
Energy Gap ◽  
Chemical Shifts ◽  
Structural Parameters ◽  
Atomic Orbital ◽  
Molecular Orbitals ◽  
Basis Sets ◽  
Nucleophilic Attack ◽  
Orbital Energy ◽  
Total Electron Density ◽  
Total Electron

The geometry of 3-trifluoromethylphenylchloroformate (FMPCF) was optimized with B3LYP method using 6–311++G** and cc–pVTZ basis sets. The molecular structural parameters and thermodynamic properties of the compound have been determined. The vibrational frequencies of the fundamental modes of the compound have been precisely assigned, analyzed and the theoretical results were compared with the experimental data. The energies of important molecular orbitals of the compound are also evaluated from DFT method. The Frontier orbital energy gap (ELUMO–EHOMO) is found to be 6.2143 eV. The extreme limits of the electrostatic potential is +8.301e × 10–3 to –8.301e × 10–3 while the total electron density spreads between +3.835e × 10–2 to –3.835e × 10–2. 1H NMR and 13C NMR chemical shifts are measured and compared with their gauge independent atomic orbital (GIAO) calculated values. The n(O7) →π*(C13–O14) and π(C1–C6) →π*(C2–C3) transitions are best stablized with 48.40 and 21.03 kcal mol–1, respectively. In 3-trifluoromethylphenylchloroformate, the atoms C13 is favourable for electrophilic attack. The atoms C2 and C8 are more favourable for nucleophilic attack. The dual descriptors (Δfk, Δsk and Δωk) revealed that the order of nucleophilic attack is C1 > C4 > C2 > C8 > C5. Thus, the present investigation provides complete structure, vibrations and reactivity characteristics of the compound.

scholarly journals Unconstrained and X-ray constrained extremely localized molecular orbitals: analysis of the reconstructed electron density

2014 ◽  
Vol 70 (6) ◽  
pp. 532-551 ◽  
Author(s):  
Leonardo H. R. Dos Santos ◽  
Alessandro Genoni ◽  
Piero Macchi
Keyword(s):  
Dipole Moments ◽  
Topological Analysis ◽  
Molecular Orbitals ◽  
Basis Sets ◽  
Electron Densities ◽  
X Ray ◽  
Localized Molecular Orbitals ◽  
New Strategy ◽  
Electron Distributions ◽  
Detailed Assessment

The recently developed X-ray constrained extremely localized molecular orbital (XC-ELMO) technique is a potentially useful tool for the determination and analysis of experimental electron densities. Molecular orbitals strictly localized on atoms, bonds or functional groups allow one to combine the quantum-mechanical rigour of the wavefunction-based approaches with the easy chemical interpretability typical of the traditional multipole models. In this paper, using very high quality X-ray diffraction data for the glycylglycine crystal, a detailed assessment of the capabilities and limitations of this new method is given. In particular, the effects of constraining the ELMO wavefunctions to experimental X-ray structure-factor amplitudes and the ability of the method to reproduce benchmark electron distributions have been accurately investigated. Topological analysis of the XC-ELMO electron densities and of the zero-flux surface-integrated charges and dipole moments shows that the new strategy is already reliable, provided that sufficiently flexible basis sets are used. These analyses also raise new questions and call for further improvements of the method.

A comparative theoretical study of the electronic structure of some nickel(II) azides, thiocyanates, and isothiocyanates

1998 ◽  
Vol 76 (7) ◽  
pp. 1006-1014 ◽  
Author(s):  
R H Abu-Eittah ◽  
M El-Esawy ◽  
N Ghoneim ◽  
A T Aly
Keyword(s):  
Electronic Structure ◽  
Electronic Structures ◽  
Theoretical Study ◽  
Molecular Orbitals ◽  
Basis Sets ◽  
Theoretical Treatment ◽  
Double Zeta ◽  
Experimental Values ◽  
Scf Calculations ◽  
Split Valence

The electronic structure, conformation, and molecular orbitals of some nickel(II) azides, thiocyanates, and isothiocyanates have been studied. Three different basis sets: split valence (SV), split valence with six d-Gaussians (SV6D), and double zeta (DZ) sets, were used to find the best ground state for nickel. It has been found that the combination, DZ-3F, gives results closest to the experimental values. The electronic structures of the nickel azides studied were completely different from those of the nickel thiocyanates. On the other hand, the electronic structures of the nickel thiocyanates studied were highly comparable to those of the corresponding nickel isothiocyanates. Molecular orbitals were computed for the complexes studied and the types of electronic transitions expected were identified and discussed.Key words: Ni(II) azides, thiocyanates, and isothiocyanates: ab initio SCF calculations; MO calculations on some Ni(II) complexes; theoretical treatment of some Ni(II) ions and salts; geometry and energetics of some nickel(II) azides, thiocyanates, and isothiocyanates.

On the use of local basis sets for localized molecular orbitals

1980 ◽  
Vol 57 (2) ◽  
pp. 169-178 ◽  
Author(s):  
Hermann Stoll ◽  
Gerhard Wagenblast ◽  
Heinzwerner Preuβ
Keyword(s):  
Molecular Orbitals ◽  
Basis Sets ◽  
Localized Molecular Orbitals ◽  
Local Basis ◽  
Local Basis Sets

Effect on frontier molecular orbitals of substituents in 5-position of uracil base pairs in vacuum and water

2017 ◽  
Vol 16 (07) ◽  
pp. 1750066 ◽  
Author(s):  
Ayhan Üngördü ◽  
Nurten Tezer
Keyword(s):  
Density Functional ◽  
Dft Method ◽  
Molecular Orbitals ◽  
Basis Sets ◽  
Frontier Molecular Orbitals ◽  
Base Pairs ◽  
Band Theory ◽  
Functional Theory ◽  
Single Nanowires ◽  
Uracil Base

The most stable structure of 5-substituted uracil base pairs and metal-mediated-5-substituted uracil complexes are determined. Density functional theory (DFT) method is used in the calculations which are carried out both in vacuum and water. LANL2DZ and 6–311[Formula: see text]G(d,p) basis sets are used for metals and the rest atoms, respectively. Effects on frontier molecular orbitals and energy gaps of substituents in 5-position of uracil base pairs in vacuum and water are found. Conductivity of base pairs or complexes are investigated for single nanowires studied by band theory. It is expected that this study will be an example for future studies that require new nanotechnological applications.

Molecule intrinsic minimal basis sets. I. Exact resolution ofab initiooptimized molecular orbitals in terms of deformed atomic minimal-basis orbitals

2004 ◽  
Vol 120 (6) ◽  
pp. 2629-2637 ◽  
Author(s):  
W. C. Lu ◽  
C. Z. Wang ◽  
M. W. Schmidt ◽  
L. Bytautas ◽  
K. M. Ho ◽  
...  
Keyword(s):  
Molecular Orbitals ◽  
Basis Sets ◽  
Minimal Basis ◽  
Exact Resolution

scholarly journals Electronic Structures of Homodinuclear Platinum(II), Palladium(II) and Gold(I) Complexes Featuring Janus-type Benzoxazolin-2-ylidene Linkers

2021 ◽  
Vol 37 (1) ◽  
Author(s):  
Nguyen Van Ha ◽  
Nguyen Thi Thu Hang
Keyword(s):  
Gas Phase ◽  
Electronic Structures ◽  
Lower Energy ◽  
High Energy ◽  
Molecular Orbitals ◽  
Molecular Structures ◽  
Basis Sets ◽  
Frontier Orbitals ◽  
Metal Centers ◽  
Td Dft

Electronic structures of a series of three homodinuclear platinum(II), palladium(II) and gold(I) complexes featuring Janus-type benzoxazolin-2-ylidene bridges and N,N-diisopropyl benzimidazolin-2-ylidene auxiliary ligands have been investigated. The gas-phase molecular structures of all compounds were first optimized using B3PW91 functional and SDD/6-31G(d) combination of basis sets. The nature of their frontier orbitals were then examined. The higher energy occupied molecular orbitals are predominantly d orbital of the metal in combination with p orbital of N,N-diisopropyl benzimidazolin-2-ylidene. On the other hand, the lower energy unoccupied molecular orbitals are p orbitals of the benzoxazolin-2-ylidene. TD-DFT calculations reveal that all the complexes require high energy ultraviolet photon for excitation and photoexcitations form excited state with decreased electron density on metal centers.

On spin irreps of (1 Ii 3) 12-fold uniform NMR spin systems as invariant-based dual tensorial sets: Roles in spin physics for weight sets and their -partitional frequency catalogues

2002 ◽  
Vol 80 (9) ◽  
pp. 1069-1083 ◽  
Author(s):  
F P Temme
Keyword(s):  
Time Reversal ◽  
Spin Symmetry ◽  
Dual Group ◽  
Geometric Constraints ◽  
Basis Sets ◽  
Time Reversal Invariance ◽  
Spin Physics ◽  
Reversal Invariance ◽  
Higher Spin ◽  
Group Basis

A direct systematic approach is given to the derivation of outer M-labelled {|IM(.)>} dual (spin) irrep sets for identical n [Formula: see text] 12-fold higher Ii nuclear spin ensembles, stressing (i) the essential role of multipartite partitions in spin physics, (ii) the value of algorithmic tableaux-based decompositions in the subsequent [Formula: see text]n combinatorical modelling, and (iii) how the dual group invariants (based on time-reversal invariance) govern the auxiliary labels of specialized dual tensors. Such (uniform inner rank) dual group basis sets (spin representations) underlie both NMR and isotopomer CNP spectral weightings. Specific applications are discussed here to illustrate the value of number partitional-based designs for statistical frequencies and recent algorithmic "sst" ([Formula: see text]n)-encoding techniques in quantized spin physics of uniform higher spin sets. In addition, a democratic recoupled form of purely SU(2) × [Formula: see text]2n projective modelling for the dual group invariants (SI) is given via an augmented democratic form of Weyl time-reversal invariance (TRV), over some regular solid geometry. From simple lattice-point geometric constraints, a maximal (2n)-index limit is established for global NMR ensemble spin symmetry. PACS Nos.: 02.10De, 02.20-a, 05.36Ch, 11.30Er, 33.25+k, 33.20Vq

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