Journal ArticleDOI
Removal of core orbitals in ‘valence orbital only’ calculations
TLDR
In this article, the authors examined pseudo-potentials which approximate the formation of a valence set of basis functions which are orthogonal and non-interacting with the core, and which simulate the core in 'valence-orbital only' calculations.Abstract:
Examination is made of inner (core) and outer-shell (valence) separation in molecular orbital calculations. Assuming a set of simple Slater type functions, pseudo-potentials are examined which approximate the formation of a valence set of basis functions which are orthogonal and non-interacting with the core, and which simulate the core in ‘valence-orbital only’ calculations. The simplest form of this potential is , where Δαi is the overlap between valence orbital i and core orbital α and F αα, the diagonal element of the Fock matrix for core orbital α, is estimated from atomic X-ray terms or fitted empirically from model diatomic calculations. Errors introduced by dropping explicit consideration of core orbitals in the formation of the Fock matrix elements for valence orbitals are not small, but can be compensated for in adjustments of F αα in approximate formulations. The total energy is examined and it is found that the ‘valence-orbital only’ energy gives a rather accurate description of the system ene...read more
Citations
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An intermediate neglect of differential overlap theory for transition metal complexes: Fe, Co and Cu chlorides
TL;DR: A complete Intermediate Neglect of Differential Overlap model suitable for the examination of transition metal complexes is described in this paper, which is characterized by the inclusion of all the one-center exchange terms necessary for rotational invariance and accurate spectroscopic predictions, as well as an accurate description of integrals involving 3D atomic orbitals.
Journal ArticleDOI
SINDO1. A semiempirical SCF MO method for molecular binding energy and geometry I. Approximations and parametrization
D. N. Nanda,Karl Jug +1 more
TL;DR: In this article, a semi-empirical SCF MO method (SINDO1) at the INDO level of approximation is described, which takes an explicit account of the orthogonality of the basis set in the calculation of core-Hamiltonian elements, approximates the effect of the explicitly ignored inner shell electrons through a pseudopotential, and employs an improved treatment of the non-diagonal core elements over the prescription used earlier in SINDO method.
Journal ArticleDOI
Large-Scale Computations in Chemistry: A Bird's Eye View of a Vibrant Field.
Alexey V. Akimov,Oleg V. Prezhdo +1 more
Journal ArticleDOI
Consistent modifications of SINDO1: I. Approximations and parameters
Bernd Ahlswede,Karl Jug +1 more
TL;DR: In this article, a consistent modification, MSINDO, of the semi-empirical MO method SINDO1 is presented, where different basis sets are used for one-and two-center interactions.
References
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Journal ArticleDOI
An Extended Hückel Theory. I. Hydrocarbons
TL;DR: The Huckel theory, with an extended basis set consisting of 2s and 2p carbon and 1s hydrogen orbitals, with inclusion of overlap and all interactions, yields a good qualitative solution of most hydrocarbon conformational problems.
Journal ArticleDOI
Atomic Shielding Constants
TL;DR: In this article, simple rules are set up giving approximate analytic atomic wave functions for all the atoms, in any stage of ionization, in analogy with the method of Zener for the atoms from Li to F, and these are applied to x-ray levels, sizes of atoms and ions, diamagnetic susceptibility, etc.
Journal ArticleDOI
Approximate Self‐Consistent Molecular‐Orbital Theory. V. Intermediate Neglect of Differential Overlap
TL;DR: The Intermediate Neglect of Differential Overlap (INDO) method proposed in this article is an improvement over the CNDO method, in that atomic term-level splittings and unpaired spin distributions are better accommodated.
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