Modified neglect of differential diatomic overlap

MNDO Modified Neglect of Diatomic Differential Overlap... 

MNDDO Modified neglect of diatomic differential overlap... 

This method is valid only in the static field limit (zero frequency), which is a weakness. However, recent advances of a derived procedure (Coupled Perturbed Hartree-Fock) permit the frequency dependence of hyperpolarizabilities to be computed. The FF method mainly uses MNDO (modified neglect of diatomic differential overlap) semi-empirical algorithm and the associated parametrizations of AM-1 and PM-3, which are readily available in the popular MOPAC software package. ... 

More recently gas-phase nitration was treated theoretically with MNDO (modified neglect of diatomic differential overlap) and INDO (intermediate neglect of differential overlap) self-consistent field calculations (34). Electron transfer and radical-pair recombination were favored for the nitration of toluene and the xylenes but not for nitrobenzene, for which a classical nitration route via a tt complex was favored. The calculations could not make a distinction between the two routes in the nitration of benzene. More information is needed about these coupling reactions and how they differ in the gas and heterogeneous-solution phases. 

An alternative strategy was to develop methods wherein the two-electron integrals are parameterized to reproduce experimental heats of formation. As such, these are semi-empirical molecular orbital methods—they make use of experimental data. Beginning first with modified INDO (MINDO/1, MlNDO/2, and MINDO/3, early methods that are now little used), the methodological development moved on to modified neglect of diatomic differential overlap (MNDO). A second MNDO parameterization was created by Dewar and termed Austin method 1 (AMI), and finally, an "optimized" parametrization termed PM3 (for MNDO, parametric method 3) was formulated. These methods include very efficient and fairly accurate geometry optimization. The results they produce are in many respects comparable to low-level ab initio calculations (such as HF and STO-3G), but the calculations are much less expensive. 

Model calculations were performed on the VAMP [24], DMOL [25, 26], and CASTEP [27] modules of the Materials Studio program package from Accelrys. Full geometry optimizations and vibrational frequency analyses were carried out in all electron approximation using in DMOL the BLYP [28, 29] functional in conjunction with the double-numeric-basis set with polarization functions (DNP) and the IR models were calculated from the Hessians [30], In CASTEP the gradient-corrected (GGA) PBE [31] functional was selected for the density functional theory (DFT) computations with norm conserving and not spin polarized approach [32], In the semi-empirical VAMP method we used the PM3 parameterization [33] from the modified neglect of diatomic differential overlap (NDDO) model to obtain the Hessians for vibrational spectrum models [30],... 

Meta- Position in the Substituted Benzene Ring Minimum Energy Coordinates Modified Neglect of Differential Overlap [NDDO (Neglect of Diatomic Differential Overlap) Approximation, Method]... 

EHT, extended Huckel theory CNDO, complete neglect of differential overlap INDO, intermediate neglect of differential overlap NNDO, neglect of diatomic differential overlap SCF, self-consistent field MINDO, modified INDO ab initio, without the use of independently derived parameters. For an independent assessment of the different molecular orbital methods applied to carbocations, see Ref. 3. 

Semiempirical SCF calculations were done using the approximations NDDO (neglect of diatomic differential overlap) [18], MNDO (modified neglect of diatomic overlap) [19], INDO (intermediate neglect of differential overlap) [20], SINDO (symmetrically orthogonalized INDO [21]) [22], and CNDO (complete neglect of differential overlap) [20, 23]. Another type of approximation [24] to the ab initio method was also applied to OF2 [16]. 

H = Hiickel, EH = extended Hiickel, PPP = Pariser-Pople-Parr, CNDO = complete neglect of differential overlap, INDO = intermediate neglect of differential overlap, NDDO = neglect of diatomic differential overlap, MNDO = modified neglect of differential overlap, MINDO = modified intermediate neglect of differential overlap. Note AMI and PM3 are MNDO methods that differ only in the way constants are chosen to approximate various integrals. 

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... 

Various theoretical methods (self-consistent field molecular orbital (SCF-MO) modified neglect of diatomic overlap (MNDO), complete neglect of differential overlap (CNDO/2), intermediate neglect of differential overlap/screened approximation (INDO/S), and STO-3G ab initio) have been used to calculate the electron distribution, structural parameters, dipole moments, ionization potentials, and data relating to ultraviolet (UV), nuclear magnetic resonance (NMR), nuclear quadrupole resonance (NQR), photoelectron (PE), and microwave spectra of 1,3,4-oxadiazole and its derivatives <1984CHEC(6)427, 1996CHEC-II(4)268>. 

A variety of more advanced, all-electron methods of this type Me available, and are generally referred to as semi-empirical calculations. The acronyms used to name the individual methods are descriptive of the manner in which atomic overlap calculations are performed. Among the more widely used semi-empirical methods are those of complete neglect of differential overlap (CNDO/2) (12), modified intermediate neglect of differential overlap (MINDO/3) (13), and modified neglect of diatomic overlap (MNDO) (14). 

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