Minimal basis-set SCF-MO calculations on aggregates of lithium and beryllium atoms

1986 ◽  
Vol 19 (9) ◽  
pp. 1253-1259 ◽  
Author(s):  
A K Ray
Keyword(s):  
Basis Set ◽  
Mo Calculations ◽  
Minimal Basis

Ab initio calculations on tetramethoxymethane

1988 ◽  
Vol 66 (8) ◽  
pp. 2041-2044 ◽  
Author(s):  
R. J. McEachern ◽  
J. A. Weil ◽  
P. G. Mezey
Keyword(s):  
Dipole Moment ◽  
Ab Initio ◽  
Electron Diffraction Study ◽  
Energy Difference ◽  
The Other ◽  
Geometric Configuration ◽  
Basis Set ◽  
Mo Calculations ◽  
Minimal Basis ◽  
Atom System

Minimal basis set ab initio SCF-MO calculations were performed on the 21-atom system of tetramethoxymethane (tetramethyl orthocarbonate). The geometric configuration of this model was optimized in two conformations, one having quasi-S4 symmetry and the other D2d symmetry. The S4 conformation was found to be 8 kJ mol−1 lower in energy than the D2d conformation, at the STO-3G level. The calculated energy difference is consistent with the recently measured geometric configuration of crystalline tetrabenzyl orthocarbonate. The calculated values of the bond lengths and angles were compared to the results of an electron diffraction study of the methyl species, and agree well with experiment. The theoretical electric dipole moment was calculated to be 0.01 D.

scholarly journals Pentagon functions for scattering of five massless particles

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
D. Chicherin ◽  
V. Sotnikov
Keyword(s):  
Phase Space ◽  
Numerical Evaluation ◽  
Public Library ◽  
Basis Set ◽  
Particle Scattering ◽  
Minimal Basis ◽  
Feynman Integrals ◽  
Analytic Expressions ◽  
Transcendental Functions ◽  
Branch Cuts

Abstract We complete the analytic calculation of the full set of two-loop Feynman integrals required for computation of massless five-particle scattering amplitudes. We employ the method of canonical differential equations to construct a minimal basis set of transcendental functions, pentagon functions, which is sufficient to express all planar and nonplanar massless five-point two-loop Feynman integrals in the whole physical phase space. We find analytic expressions for pentagon functions which are manifestly free of unphysical branch cuts. We present a public library for numerical evaluation of pentagon functions suitable for immediate phenomenological applications.

scholarly journals Topological Effect on MO Energies, IX. On Topologically Related 1,4-Dibora-2,3-diazarine and 1,4-Dibora-2,5-diazarine

1984 ◽  
Vol 39 (8) ◽  
pp. 1053-1057 ◽  
Author(s):  
loan Motoc ◽  
Oskar E. Polansky
Keyword(s):  
Basis Set ◽  
Complete Agreement ◽  
Mo Calculations ◽  
Symmetry Constraint ◽  
Topological Effect ◽  
Equilibrium Geometries

AbstractMinimal STO-NG (N = 3, 4 and 6 ) basis set non-empirical HF SCF MO calculations have been performed for topologically related 1,4-dibora-2,3-diazarine (S) and 1,4-dibora-2,5-diazarine (T). The equilibrium geometries of these S and T isomers have been computed by symmetry-constraint geometry optimizations using the STO-3G basis set. The calculations lead to the prediction that: i) the T isomer is about 48 kJ/mole less stable than the S isomer, and ii) the π -MO energy patterns of the S and T isomers are in complete agreement with the TEMO theorem, while the bonding σ-MO eigenvalues exhibit four inversion points.

Etude théorique de la structure et de la réactivité de l'anion du pentazole

1983 ◽  
Vol 61 (7) ◽  
pp. 1435-1439 ◽  
Author(s):  
Minh-Tho Nguyen ◽  
Michel Sana ◽  
Georges Leroy ◽  
Jose Elguero
Keyword(s):  
Molecular Nitrogen ◽  
Activation Energies ◽  
Basis Set ◽  
Etude Théorique ◽  
Mo Calculations ◽  
Étude Théorique ◽  
Azide Ion ◽  
Synthetic Target ◽  
Stable Structures

"Abinitio" LCAO-SCF-MO calculations using the 4-31G basis set were carried out in order to study the supersystem [Formula: see text]. The three possible stable structures (azide ion + molecular nitrogen, pentazene ion, and pentazole ion) and their reactions paths were calculated. The pentazole anion is less stable than the reagents [Formula: see text], but much more stable than the pentazene anion; it could constitute a reasonable synthetic target. The activation energies of the different paths were compared with those of the neutral supersystem N5H.

The structure and energetics of low-lying states of RCO and RNN free radicals

1977 ◽  
Vol 55 (5) ◽  
pp. 863-868 ◽  
Author(s):  
N. Colin Baird ◽  
Harish B. Kathpal
Keyword(s):  
Experimental Data ◽  
Free Radicals ◽  
Hydrogen Atom ◽  
Ab Initio ◽  
Open Shell ◽  
Basis Set ◽  
Basis Sets ◽  
Mo Calculations ◽  
Decomposition Products ◽  
Ab Initio Mo Calculations

The important geometrical variables in the structures of the lowest 2A′ and 2A′′ states of the free radicals HCO, CH3CO, NH2CO, HNN, and CH3NN have been determined by ab initio MO calculations using the STO-3G basis set. The energy differences between the states, and the energies of the radicals relative to their decomposition products and relative to their hydrogen atom addition products, are reported using both STO-3G and 4-31G basis sets in the restricted open-shell calculations. The trends in these results and their relation to available experimental data are discussed.

Calculation of electrostatic potentials and fields inside zeolite cavities

1988 ◽  
Vol 53 (10) ◽  
pp. 2308-2319 ◽  
Author(s):  
János G. Ángyán ◽  
György Ferenczy ◽  
Péter Nagy ◽  
Gábor Náray-Szabó
Keyword(s):  
Ab Initio ◽  
Lone Pair ◽  
Electrostatic Potentials ◽  
Basis Set ◽  
Mean Deviation ◽  
Minimal Basis ◽  
Approximate Methods ◽  
Monopole Approximation ◽  
Van Der Waals Surface ◽  
Modified Formula

We present a modification of our bond increment method for the calculation of molecular electrostatic potentials and fields inside zeolite cavities. Introducing a variant of the Mulliken approximation for the off-diagonal matrix elements of the potential and optimizing the parameters of the modified formula, we achieved much better agreement with ab initio STO-3G minimal basis set results than with the original version. For a representative set of 10 small molecules the standard mean deviation between potentials calculated on the van der Waals surface with the ab initio and approximate methods is 9·1 kJ/mol. The relative error decreases from 21 to 9 per cent for the lone-pair regions of molecules modelling zeolite cavities. Applying the modified bond increment method for a realistic faujausite model we have found that the potential and field are almost exclusively of long-range origin. This means that, if using appropriate atomic charges, the monopole approximation gives correct results for electrostatic potentials and fields inside zeolite cavities.

scholarly journals Random versus Systematic Errors in Reaction Enthalpies Computed Using Semiempirical and Minimal Basis Set Methods

ACS Omega ◽  
2018 ◽  
Vol 3 (4) ◽  
pp. 4372-4377 ◽  
Author(s):  
Jimmy C. Kromann ◽  
Alexander Welford ◽  
Anders S. Christensen ◽  
Jan H. Jensen
Keyword(s):  
Systematic Errors ◽  
Basis Set ◽  
Minimal Basis
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