Neglect of Differential Overlap Version

A deficiency in CNDO was soon identified, in that two neutral atoms separated by a distance of several Angstroms would still be attracted to each other. This was a result of the inequality of the elearon-core attraction and the electron-electron repulsion. To correct this, the electron-core attraction was reduced to 

An unfortunate side-effect of this change was to make the interaction between the two hydrogen atoms in triplet hydrogen repulsive at all distances. The core-core interaction in CNDO and CNDO/2 was 

Since Vab is less than I/R12 at all distances, the physically unrealistic result followed that at all distances the two hydrogen atoms would repel each 

This represents the energy required to remove an electron from atomic orbital (p in the fully ionized atom. 

An alternative, not used in CNDO, would have been to derive from the electron affinity, Ap., as 

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MINDO/3 Modified intermediate neglect of differential overlap (version 3)... 

CRF=core-repulsion function MIND03 = modified intermediate neglect of differential overlap, version 3 MNDO = modified neglect of differential overlap MNDO/d = modified neglect of differential overlap with d orbitals. 

ZINDO/I is based on a modified version of the intermediate neglect of differential overlap (INOOh which was developed by Michael /ern cr of the Quan turn Th cory Project at th e Lin iversity oIFIorida. Zerner s original IXDO/1 used the Slater orbital exponents with a distance dependence for the first rorv transition metals only. (See Thvorel. Chirn. Ada (Bed.) 53, 21-54 (1979).) However, in HyperChem con stan I orbital expon en ts are used for all the available elements, as recommended by. Anderson, Kdwards, and /.erner, /norg. Chern. 25, 2728-2732,1986,... 

Highest occupied molecular orbital Intermediate neglect of differential overlap Linear combination of atomic orbitals Local density approximation Local spin density functional theory Lowest unoccupied molecular orbital Many-body perturbation theory Modified INDO version 3 Modified neglect of diatomic overlap Molecular orbital Moller-Plesset... 

Three versions of Modified Intermediate Neglect of Differential Overlap (MINDO) models exist, MINDO/1, MINDO/2 and MINDO/3. The first two attempts at parameterizing INDO gave quite poor results, but MINDO/3, introduced in 1975, produced the first general purpose quantum chemical method which could successfully... 

Three versions of Modified Intermediate Neglect of Differential Overlap (MINDO)... 

MINDO/3 Modified Intermediate Neglect of Differential Overlap. The MINDO/3 technique representing the third version of MINDO is a semi-em-pirical all-valence electron self-consistent field molecular orbital approach. MINDO/3 calculations provide fairly accurate values of molecular properties on medium to large organic molecules. 

Ever since the introduction of the semi-empirical Extent Huckel Theoiy (EHT) by Hoffman [1] in the early 1960s and followed by the Complete Neglect of Differential Overlap (CNDO) method [2], there has been a constant evolution in the field of semi-empirical MO methods. This research has evolved into a situation where at present the computational chemist using the recent Modified Neglect of Differential Overlap (MNDO) [3] version and its more elaborate successors Austin Model (AMI) [4] and Parametrized Model (PM) [5] has a number of impressive tools at his or her disposal to describe the molecular structme and properties of molecules containing several hundreds of atoms. 

Further approximations of the Hiickel method were removed with the introduction of the complete neglect of differential overlap (CNDO) method, which is a slightly more sophisticated method for dealing with the terms H,k that appear in the secular equations for the coefficients. The introduction of CNDO opened the door to an avalanche of similar but improved methods and their accompanying acronyms, such as intermediate neglect of differential overlap (INDO), modified neglect of differential overlap (MNDO), and the Austin Model 1 (AMI, version 2 of MINDO). Software for all these procedures is now readily available, and reasonably sophisticated calculations can be run even on handheld computers. 

The polarity of the amide bond and also the interaction of the 2p electrons of N with the n-electrons of the carbonyl group are functions of the ring size and are manifested by different ionization potentials obtained by photoelectron (PE) spectroscopy. The map of the spatial electron distribution of iV-methylacetamide, obtained by CNDO/2 (COMPLETE NEGLECT OF DIFFERENTIAL OVERLAP - SECOND VERSION) and ab initio molecular orbital calculations, has... 

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