摘要:

AbstractThe enumeration of benzenoids is studied with the aid of different modifications of a computer program. Known values for the number of cata‐condensed and of all benzenoids withh(number of hexagons) up to eight are reproduced. These benzenoids are classified into (a) unbranched of different symmetries and branched cata‐condensed, and (b) normal, essentially disconnected and non‐Kekuléan peri‐condensed. Within the normal benzenoids a more detailed classification is performed: basic benzenoids, fused, or annelated. Forh= 9 an almost complete classification along the same lines was

ISSN:0192-8651    

DOI:10.1002/jcc.540080301

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractSelf‐consistent‐field‐Xα‐scattered wave calculations on clusters Si2O76−and H6Si2O7modeling silica have been performed. Incorporation of Si 3dorbitals produces significant changes in the overall valence structure. In addition to σ Si — O bonds, there exists a bonding π character due to the participation of O 2pand Si 3d. Hydrogen terminators do not seem to correct edge effects for

ISSN:0192-8651    

DOI:10.1002/jcc.540080302

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractParameters have been optimized for a potential energy function to be used in molecular mechanics calculations of small imines as a preliminary step to calculations on larger systems. A consistent force field (CFF) program was used, and a new damping algorithm due to Sundius was introduced in the optimization procedure. Optimization of parameters has been done on structural and vibrational data of five small imines and one oxime. The quality of the derived potential energy function is examined by calculations on larger oximes.

ISSN:0192-8651    

DOI:10.1002/jcc.540080303

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractModel potential parameters and valence orbitals were generated for the transition metal atoms Sc through Hg. Only thendand (n+ 1)svalence electrons were treated explicitly and the effects of the remaining electrons were replaced by model potentials. For brevity they may be calledsd‐MPs. Major relativistic effects were incorporated on the level of Cowan and Griffin's quasirelativistic Hartree‐Fock (QRHF) method for the second and third transition metal atoms. The model potential parameters and valence orbitals were determined so as to reproduce the results of the numerical Hartree‐Fock reference calculations. The obtained valence orbitals have inner nodal structure. The model potential method can yield a balanced description of thes2dn–1,sdn, anddn+ 1configurations of the atoms. The polarization functions were also generated for the use in molecular calcu

ISSN:0192-8651    

DOI:10.1002/jcc.540080304

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractModel potential parameters and valence orbitals were generated for the transition metal atoms Sc through Hg. They are named thespd‐MPs and are supplementary to thesd‐MPs presented in the preceding article. The outermost corenpelectrons were treated explicitly together with valencendand (n+ 1)selectrons, and the remaining electrons were replaced by a model potential. The model potential parameters and valence orbitals were determined in the same way as thesd‐MPs. Major relativistic effects (via the mass velocity and Darwin terms) were also incorporated in thespd‐MPs for the second‐and third‐row transition metal atoms. The results of numerical nonrelativistic Hartree‐Fock (HF) calculations for the first‐row transition metal atoms and of the quasirelativistic HF calculations with Cowan and Griffin's method for the second‐row and third‐row transition metal atoms were used as reference data in determin

ISSN:0192-8651    

DOI:10.1002/jcc.540080305

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe IPPP‐INDO method is applied to study different interactions as well as transmission mechanisms of77Se —77Se coupling constants incis‐ andtrans‐1,2‐bis(methylseleno)ethene. Preferential conformations were determined using a modified version of the PCILO‐CNDO method. The preferential conformation of the cis compound is such that nonbonding electron pairs of both Se atoms overlap to some extent. In this conformation a large and positive through‐space transmission of the Fermi contact term of the77Se —77Se coupling takes place, which strongly depends on the Se — Se distances. The similarity between this coupling and others involving different nuclei is discussed. The total calculated coupling is in fair agreement with experimental values for similar compounds. The77Se —77Se coupling in the trans‐compound is largely dominated by the orbital interaction, which is mainly transmitted through the vi

ISSN:0192-8651    

DOI:10.1002/jcc.540080306

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe quantum mechanical perturbation method has been utilized to explain the biological function of 8‐azapurine nucleoside analogs. The possibility of binding of the analog has been discussed in terms of interaction energy, which includes the electrostatic, polarization, dispersion, and repulsion terms. The stacking and the hydrogen bonding energy of the analog with nucleic acid bases and base pairs have been computed in all possible orientations. The model developed by Sanyal et al. for the incorporation of nucleoside analogs has been used to find out the inhibitory effect of the drug on nucleic acid and protein synthesis. It has been observed that these results are in broad agreement with the experimental observation

ISSN:0192-8651    

DOI:10.1002/jcc.540080307

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY