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 Quasi-Atomic Bond Analyses in the Sixth Period: I. Relativistic Accurate Atomic Minimal Basis Sets for the Elements Cesium to Radon

2019 ◽  
Vol 123 (25) ◽  
pp. 5242-5248 ◽  
Author(s):  
George Schoendorff ◽  
Aaron C. West ◽  
Michael W. Schmidt ◽  
Klaus Ruedenberg ◽  
Mark S. Gordon
Keyword(s):  
Basis Sets ◽  
Minimal Basis

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.

Molecule intrinsic minimal basis sets. II. Bonding analyses for Si4H6 and Si2 to Si10

2004 ◽  
Vol 120 (6) ◽  
pp. 2638-2651 ◽  
Author(s):  
W. C. Lu ◽  
C. Z. Wang ◽  
M. W. Schmidt ◽  
L. Bytautas ◽  
K. M. Ho ◽  
...  
Keyword(s):  
Basis Sets ◽  
Minimal Basis

The simplified ab initio method calculation of linear polarizability

1973 ◽  
Vol 26 (5) ◽  
pp. 921 ◽  
Author(s):  
RD Brown ◽  
GR Williams
Keyword(s):  
Ab Initio ◽  
Small Molecules ◽  
Basis Set ◽  
Basis Sets ◽  
Orbital Method ◽  
Polarizability Anisotropy ◽  
Minimal Basis ◽  
Hartree Fock ◽  
Numerical Performance ◽  
Experimental Values

The simplified ab-initio molecular-orbital method described previously is particularly suited to the calculation of polarizabilities by the non-perturbative coupled Hartree-Fock technique. Trial calculations on CO and HF, for which comparison with corresponding ab-initio calculations is possible, show that the method gives an adequate numerical performance. Minimal basis set calculations in general tend to give values that are considerably too low because of inadequate flexibility of the basis and this is the origin of the large discrepancy between theory and experiment, especially for small molecules. ��� Results are also reported for N2O and O3. For these larger systems the SAI results with minimal basis sets are noticeably nearer experimental values. The polarizability anisotropy for N2O is particularly well reproduced by the SAI method. �

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