Semiempirical MSINDO

The semiempirical molecular orbital (MO) methods of quantum chemistry [1-12] are widely used in computational studies of large molecules. A number of such methods are available for calculating thermochemical properties of ground state molecules in the gas phase, including MNDO [13], MNDOC [14], MNDO/d [15-18], AMI [19], PM3 [20], SAMI [21,22], OM1 [23], OM2 [24,25] MINDO/3 [26], SINDOl [27,28], and MSINDO [29-31]. MNDO, AMI, and PM3 are widely distributed in a number of software packages, and they are probably the most popular semiempirical methods for thermochemical calculations. We shall therefore concentrate on these methods, but shall also address other NDDO-based approaches with orthogonalization corrections [23-25],... 

All semiempirical methods are parameterized for the elements H, C, N, F, and O which form the basis of most organic molecules that are of importance in pharmaceutics, biochemistry, and organic chemistry. Here it is possible to compare the statistical errors for some of the more recent methods. In Table 1, the statistics for energetic, structural, and electronic properties for first-row elements are compared for MSINDO, MNDO, AMI, and PM3. 

The following subsections will present a selection of applications of the most frequently used semiempirical methods INDO/S (or ZINDO), MSINDO (or SINDOl), MNDO and MNDO/d, AMI, PM3, and SAMI and modifications of these methods... 

A possible explanation of the trends shown in Fig. 5 is that wherever high accuracy is required, semiempirical methods have recently been replaced by DFT approaches, unless they are designed for the description of certain properties (like INDO/S) or classes of materials (like MSINDO). 

Recognizing the importance of orthogonalization effects (see Section 2.38.2.6), which are neglected in many semiempirical SCF MO methods, INDO-based methods with orthogonalization corrections, SINDO, SINDO1 and MSINDO, " have been developed. The orthogonalization models... 

SINDOl is a semiempirical method based on the INDO model and derives its name from an approximate transformation to symmetrieally orthogonalized orbitals. Since the new version of this method, MSINDO (see Section 2.38.3.6), is more accurate, should be used instead of SINDOl. 

In the next section we discuss MSINDO semiempirical and HF nonempirical methods implementation of COM for the calculation of bulk properties of rutile crystal. The efficiency of the MSINDO method will be demonstrated that gives reasonable agreement with the results of HF calculations and at the same time is essentially simpler in practical reaUzation. 

The cyclic-cluster approach was implemented in the semiempirical SCF-MO method SINDOl [319] and its recent modification MSINDO [301] and has been successfully applied for bulk and surface properties of oxides [302,320]. 

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