Spectral properties of minimal-basis-set orbitals: Implications for molecular electronic continuum states

2005 ◽  
Vol 102 (5) ◽  
pp. 948-955 ◽  
Author(s):  
P. W. Langhoff ◽  
C. L. Winstead
Keyword(s):  
Spectral Properties ◽  
Basis Set ◽  
Molecular Electronic ◽  
Minimal Basis ◽  
Continuum States

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.

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

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.

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