摘要:

AbstractAn algorithm based on a small matrix approach to the solution of a system of inhomogeneous linear algebraic equations is developed and tested in this short communication. The solution is assumed to lie in an initial subspace and the dimension of the subspace is augmented iteratively by adding the component of the correction vector obtained from the Jacobi scheme on the coefficient matrixA(ATA, if the matrixAis nondefinite) that is orthogonal to the subspace. If the dimension of the subspace becomes inconveniently large, the iterative scheme can be restarted. The scheme is applicable to both symmetric and nonsymmetric matrices. The small matrix is symmetric (nonsymmetric), if the coefficient matrix is symmetric (nonsymmetric). The scheme has rapid convergence even for large nonsymmetric sparse systems.

ISSN:0192-8651    

DOI:10.1002/jcc.540110502

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractFloating spherical Gaussian orbitals are used within a split‐shell description to calculate the properties of H, He, He+, H2, H+2, HeH+, and H+3in a strong uniform electric field. Accurate polarizabilities including their field strength dependence are obtained with two basis functions at most. Critical field strengths for ionization and deprotonation are determined for different orientations of molecules. Electron tunneling is described within the time dependent approach using floating Gaussian orbitals als

ISSN:0192-8651    

DOI:10.1002/jcc.540110503

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractNormal coordinate calculations have been performed for urea and deuterated urea in the crystalline state. We have used the modified Urey–Bradley–Shimanouchi intramolecular potential energy function and a rather sophisticated intermolecular energy function to reproduce I.R. and Raman frequencies with an average error of 2 cm–1. The general agreement between the calculation and experiment suggests that intermolecular interactions must be taken into account to determine reliable intramolecular parameters of the potential energy function, mainly the barrier to internal rotation around the CN bond. The intermolecular energy function, which consists of the Buckingham function and an explicit harmonic function for hydrogen‐bonding, then has the merit to reproduce quite well the observed frequencies of lattice v

ISSN:0192-8651    

DOI:10.1002/jcc.540110504

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe hypolipidemic activities of phthalimide and seven related compounds are subjected to a QSAR analysis based on results from AM1 molecular orbital calculations. Least‐squares fits show a correlation of the activities with LUMO energies and carbonyl polarities and predict enhanced activities for two new phthalimide derivative

ISSN:0192-8651    

DOI:10.1002/jcc.540110505

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractEntropy and solvent effects are calculated for some conformations of Ala‐Gly. The inclusion of these effects in energy calculations show the βIItype structure to be the most stab

ISSN:0192-8651    

DOI:10.1002/jcc.540110506

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractAn extension of the Indirect Counterpoise (ICP) method, proposed in previous work, has been applied to the H2OHF hydrogen‐bonded system. The new version, which introduces important numerical changes is called EICP (Extended Indirect Counterpoise method). In their framework, the nonnegligible overestimation of the Counterpoise correction (CP) of Boys and Bernardi in the coupling component (MIX) of the interaction energy, computed via the Kitaura and Morokuma method is studied. Several basis sets, BS, were used to describe the oxygen, fluorine and hydrogen atoms that constitute the complex. The EICP results leads to more coherent values with the uncorrected energy than with the CP correction, which seems to be significantly affected by the size and type of the basis set used (especially for minimal basis se

ISSN:0192-8651    

DOI:10.1002/jcc.540110507

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractAlgorithms and computer codes in FORTRAN 77 are developed for the computation of characters of generalized wreath product groups through generating function methods. Characters of generalized wreath product groups of symmetric groups are computed in terms of the characters of much smaller composing groups using plethysms ofS‐functions. The developed codes were tested for many generalized wreath product groups. The character tables of generalized wreath products,S2[S3,S2,S2] (NMR group of hexane) andS4[S3] containing 576 and 31,104 elements, respectively, were constructed as example

ISSN:0192-8651    

DOI:10.1002/jcc.540110508

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractA new method is presented for defining a smooth, triangulated analytic surface for biological molecules. The surface produced by the algorithm is well‐suited for use with a recently developed polarizationcharge technique1for the computation of the electrostatic potential of solvated molecules, and may also be used for calculations of molecular surface areas and volumes. The new method employs Connolly's definitions of contact, reentrant and saddle surface,2but includes modifications that preclude the presence of self‐interesting reentrant surface, and also insure a rigorous decomposition of contact regions into curvilinear finite elements. The triangulation algorithm may be used in conjunction with the electrostatic methods described previously to compute the electric potential of molecules of arbitrary shape in solution. Applications include the estimation of hydration enthalpies, computation of the electrostatic forces associated with solvation, estimation of interactions between separate charged species in solution, and computation of the three‐dimensional form of the molecular electric potential. Test calculations are presented for a double‐stranded dinucleotide, the polypeptide enkephalin, and the protein fer

ISSN:0192-8651    

DOI:10.1002/jcc.540110509

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe completely optimized structure and harmonic force field ofs‐trans‐buta‐1,3‐diene are reported at the MP2/6‐31G and MP2/6‐31G* levels of computation. Sets of empirical scale factors for the calculated force fields are derived and compared with the corresponding values computed at the RHF/4‐31G and RHF/6‐31G levels. Changes in the scale factors for this series of force fields are discussed. The vibrational frequencies are also reported for thirteen isotopomers ofs‐trans‐buta‐1,3‐diene using the MP2/6‐31G* force field. Some characteristics of thegaucheandcisforms of buta

ISSN:0192-8651    

DOI:10.1002/jcc.540110510

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY

摘要:

AbstractAn analytical procedure is presented for the determination of the proper dissociation configurations of a molecule. We illustrate this procedure by determining the proper dissociation configurations of many electronic states of the first‐row diatomic molecules and ozone. Finally, a few simple guidelines are provided to help in the identification of the important configurations needed for proper dissociation of a molecul

ISSN:0192-8651    

DOI:10.1002/jcc.540110511

出版商:John Wiley&Sons, Inc.    

年代:1990

数据来源: WILEY