ZINDO

The Zerner s INDO method (ZINDO) is also called spectroscopic INDO (INDO/S). This is a reparameterization of the INDO method specifically for the purpose of reproducing electronic spectra results. This method has been found to be useful for predicting electronic spectra. ZINDO is also used for modeling transition metal systems since it is one of the few methods parameterized for metals. It predicts UV transitions well, with the exception of metals with unpaired electrons. However, its use is generally limited to the type of results for which it was parameterized. ZINDO often gives poor results when used for geometry optimization. 

Comparing the core-core repulsion of the above two equations with those in the MNDO method, it can be seen that the only difference is in the last term. The extra terms in the AMI core-core repulsion define spherical Gaussian functions — the a, b, and c are adjustable parameters. AMI has between two and four Gaussian functions per atom. 

These are the only differences between the MNDO and AMI functional form. Dewar s group regenerated AMI parameters for the elements H, B, C, N, 0, F, Al, Si, P, S, Cl, Zn, Ge, Br, and Sn and found that the main gains in AMI over MNDO were the ability to reproduce hydrogen bonds and the promise of better activation energies for reactions. AMI does not significantly change the computation time compared with MNDO. 

ZINDO/1 is based on a modified version of the intermediate neglect of differential overlap (INDO), which was developed by Michael Zerner of the Quantum Theory Project at the University of Florida. Zerner s original INDO/1 used the Slater orbital exponents with a distance dependence for the first row transition metals only. (See Theoret. Chim. Acta (Berl.) 53, 21-54 (1979).) However, in HyperChem constant orbital exponents are used for all the available elements, as recommended by Anderson, Edwards, and Zerner, Inorg. Chem. 25, 2728-2732,1986. 

As with the other semi-empirical methods, HyperChem s implementation of ZINDO/1 is restricted to spin multiplicities up to a quartet state. ZINDO/1 lets you calculate the energy states in molecules containing transition metals. 

HyperChem s implementation of ZINDO/1 has been tested using parameters suggested by references to work done by Zerner on first row transition metals. 

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After yon choose the com pn tat ion method and options, you can use Start bog on the file menu to record results, such as total energies, orbital en ergies, dipole m om en Ls, atom ic charges, en Lhalpics of formalion (foritieCNDO, IN DO, MIXDO/3, MNDO, AMI, PM3, ZINDO/1, and ZINDO/S mclh ods), etc. 

ZINDO/S is an INDO method paramcteri/ed to reproduce LV visible spectroscopic transitions when used with the singly excited Cl method. It w as developed in the research group of Michael Zerner of the Quantum fheory Project at the University of Florida. 

The basic equations of ZINDO/1 are the same as those m IXDO, except I orL i y. In stead of usiri g th e electron egativity in INDO, ZlNDO/l uses th e ion i,ration potential for computing Llj,... 

The mixed model used m ZINDO/1 is identical to that used in CXDO an d INDO if there is no d-orbital in volved in the t iian turn... 

The algorithms in Z[ DO/S are almost the same as those in ZlNDO/1, except of the one-center two-electron integral, b . ZINDO/S uses em pirical value of in stead of ii sin g ah initio vaine in terms of the Slater orbitals. 

ZlNDO/S is differen t from ZINDO/1 because th ey use differen t algorithms in computing the Coulomb integrals. Hence the two et uation s used in th e rn ixed m odel in ZINDO/1 are also employed... 

The one exception to this is the INDO/S method, which is also called ZINDO. This method was designed to describe electronic transitions, particularly those involving transition metal atoms. ZINDO is used to describe electronic excited-state energies and often transition probabilities as well. 

Intensities for electronic transitions are computed as transition dipole moments between states. This is most accurate if the states are orthogonal. Some of the best results are obtained from the CIS, MCSCF, and ZINDO methods. The CASPT2 method can be very accurate, but it often requires some manual manipulation in order to obtain the correct configurations in the reference space. 

ZINDO is an adaptation of INDO speciflcally for predicting electronic excitations. The proper acronym for ZINDO is INDO/S (spectroscopic INDO), but the ZINDO moniker is more commonly used. ZINDO has been fairly successful in modeling electronic excited states. Some of the codes incorporated in ZINDO include transition-dipole moment computation so that peak intensities as well as wave lengths can be computed. ZINDO generally does poorly for geometry optimization. 

The semiempirical techniques available include EH, CNDO, INDO, MINDO/3, ZINDO, MNDO, AMI, and PM3. The ZINDO/S, MNDO/d, and PM3(TM) variations are also available. The semiempirical module seems to be rather robust in that it did well on some technically difficult test calculations. 

Configuration Interaction (or electron correlation) improves energy calculationsusing CNDO, INDO, MINDO/3, MNDO, AMI, PM3, ZINDO/1, and ZINDO/Sfor these electron configurations... 

In order to conserve the total energy in molecular dynamics calculations using semi-empirical methods, the gradient needs to be very accurate. Although the gradient is calculated analytically, it is a function of wavefunction, so its accuracy depends on that of the wavefunction. Tests for CH4 show that the convergence limit needs to be at most le-6 for CNDO and INDO and le-7 for MINDO/3, MNDO, AMI, and PM3 for accurate energy conservation. ZINDO/S is not suitable for molecular dynamics calculations. 

CNDO, INDO, MINDO/3, ZINDO/1, and ZINDO/S Methods... 

ZINDO/1 and ZINDO/S are Dr. Michael Zerner s INDO versions and used for molecular systems with transition metals. ZINDO/1 is expected to give geometries of molecules, and ZINDO/S is parametrized to give UV spectra. 

The ZINDO/1 method is the most suitable semi-empirical method in HyperChem for determining structures and energies of molecules with first or second transition row metals. 

ZINDO/S is parameterized to reproduce spectroscopic transitions, therefore we do not recommend using this method for geometry optimization. You can obtain better results by performing a singlepoint calculation with ZINDO/S on a geometry obtained from the Model Builder, an optimization using one of HyperChem s other methods, or an external source. 

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