Quantum mechanics MOPAC

NBO, GAUSSIAN, SPARTAN, MOPAC, Standalone software programs (workstation versions) quantum mechanical ... 

MOPAC is a general-purpose semiempirical molecular orbital program for the study of chemical structures and reactions. It is available in desktop PC running Windows, Macintosh OS, and Unix-based workstation versions. It uses semiempirical quantum mechanical methods that are based on Hartree-Fock (HF) theory with some parameterized functions and empirically determined parameters replacing some sections of the complete HF treatment. The approximations in... 

Extensive catalog of programs for quantum mechanics, molecular mechanics, and molecular graphics, including DRAW (a graphical complement to MOPAC), AMPAC, MM2, CNINDO/D, FORTICON8 (Extended Hiickel), MNDO, HAM/3, POLYATOM, MOLVIEW, NAMOD, etc. PC and Mac-II. 

The MOPAC program (Molecular Orbital PACkag) (26) Is one of the popular quantum mechanical semiempirical methods. The AM1 (Austin Model 1), developed by Michael Dewar (26), is a generalization of the modified neglect of differential diatomic overlap (MNDO) approximation. Often, AM1 is implemented in the MOPAC, and MOPAC(AMt) has been widely used to minimize molecular conformations, to calculate electronic configuration, and to predict such properties as electron distribution and partial charges. 

Quantum-Mechanical Continuum Solvation Models. Several ab initio continuum solvation models were discussed in Section 15.22. One can calculate AG, , by such SCRF methods as the dipole-in-a-sphere, the multipole expansion, or the PCM methods using semiempirical methods such as AMI or PM3 instead of an ab initio electronic-structure method. Thus the program MOPAC-93 implements the PCM calculation of solvent effects with semiempirical methods and the program AMPAC 6.0 implements the COSMO method. 

Table 3. Quantum mechanical calculation of the ionization potential (IP) of some alkyl substituted phenols (AMI Hamiltonian, MOPAC 93, available from FUJITSU Ltd. together with the interface from CambridgeSoft Corporation information concerning AMI is given in the text below) [52]...

The last point has been studied more quantitatively for the electrolyte Li02CCHj,Fy (jc+y=3) / DMSO [97,105]. Semiempirical quantum-mechanical calculations with the help of MOPAC [143] show that the mean electron density at the oxygen atoms (O) decreases for these acetates by about 0.1 unit with increasing fluorine content of the anion [97]. As a consequence ... 

Structure building, manipulation, energy minimization and molecular dynamics, protein loop searching, MOPAC interface. INSIGHT is an interactive graphics front-end to the empirical energy calculations of DISCOVER. DMoI for quantum mechanical density functional theory calculations. DelPhi for electrostatic potential maps. 

Recently, Dunmur et al. [57] have calculated the energy-minimised structures and rotational energy barriers for a number of chiral dopants using the MM2 force field and the techniques discussed above. In this work MM2 structures were further refined using the semi-empirical SCF quantum mechanical program MOPAC [62] (Sec. 3.1.3). Their results are shown in Fig. 6. 

The partial charges were derived from semi-empirical quantum - mechanical calculations using MOPAC 6.0 with the AMI Hamiltonian [12]. Due to computational limitations, the partial charges of the macrocyclic core and of the ester substituents were calculated separately. The final charge set is shown in fig. 1. The benzene of crystallisation was included using CHARMM 22 parameters [13]. A full list of the parameters will be published elsewhere. 

To study the possible reasons and elementary mechanisms of the catalytic activity of CPs, we have modeled the electronic structure of some molecular CPs clusters and its adsorption complexes with oxygen. A MOPAC computer complex and, in particular, the PM3 quantum-chemical program of this complex was used for calculations. The results of calculations have shown that both oxygen atoms form bonds with two more active carbon atoms of CP molecular cluster (so-called bridge model of adsorption). The total energy of system after chemical adsorption at such active atoms is minimal (Fig. 2). 

Figure 22 Number of publications per year in the CJACS file mentioning Quantum Chemistry Program Exchange and two programs it distributes, MM2 and MOPAC. The queries used to search the CJACS file were (1) qcpe or quantum(w)chemis-try(w)program(w)exchange, (2) (qcpe or quantum(w)chemistry(w)program(w)ex-change) and mopac, and (3) (qcpe or quantum(w)chemistry(w)program(w)exchange) and (mm2 and (force(w)field or molecular(w)mechanics)).

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