ZINDO/S

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 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. 

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. 

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. 

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. 

The CNDO/INDO, MINDO/3, Z3NDO/1, and ZINDO/S methods might be expected to imply an even simpler equation for the electron density than the above. For example, a rigorous complete neglect of CNDO approximation, suggests that equations (87) and (88) should be replaced by expressions with a sum only over diagonal elements of the density matrix. This would represent a molecular charge density that is the exact sum of atomic densities. Alter-... 

HyperChem currently supports one first-principle method ab initio theory), one independent-electron method (extended Hiickel theory), and eight semi-empirical SCFmethods (CNDO, INDO, MINDO/3, MNDO, AMI, PM3, ZINDO/1, and ZINDO/S). This section gives sufficient details on each method to serve as an introduction to approximate molecular orbital calculations. For further details, the original papers on each method should be consulted, as well as other research literature. References appear in the following sections. 

For geometry optimizations and comparison of total energies (which should be carried out with ZINDO/1, not ZINDO/S), both overlap weighting factors (Sigma-Sigma and Pi-Pi) should be set to 1 in the Semi-empirical Options dialog box. 

ZINDO/S is different from ZINDO/I because they use different algorithms in computing the Coulomb integrals. Hence the two equations used in the mixed model in ZINDO/1 are also employed... 

These models were developed by Zerner and coworkers (Zerner, Anderson, and Edwards, 1986). ZINDO/1 is a variant of INDO, and ZINDO/S is an INDO method designed to predict spectroscopic transitions. 

The tautomerism of 4 (Figure 1) was also studied by UV-Vis (ultraviolet-visible) spectroscopy in polar aprotic solvents the effect of added water, darkness, and indirect sunlight were also evaluated. The experimental spectroscopic results are discussed in Section 13.14.3.1.1 (i). Theoretical calculations using ZINDO/S were performed to state the allowed absorption transitions <2005SAA875>. The five tautomeric structures of 4 as well as the calculated energies for each are depicted in Figure 2. 

The superposition of the calculated transitions corresponding to all the tautomers (Figure 2) reproduces satisfactorily the entire experimental spectrum. The low-intensity transition observed experimentally in the range 350-450 nm is predicted as forbidden in ZINDO/S calculations. The comparison between these calculations allowed transitions and the experimental absorption spectrum (see Section 13.14.3.1.1 (i)) leads to the assumption that the TtJt band located between 250 and 330 nm belongs principally to tautomers 4 and 7 (thione form). 

Table 6.5 Calculated and experimental [114] UV spectra of methylenecyclopropene. The semiempirical calculations were done with ZINDO/S in G94W the ab initio results are from Table 5.16...

---