Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    A multireference valence bond approach to electronic excited states (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 2917-2925 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new spin coupled multireference balence bond scheme for the treatment of electronic excited states is presented. The method involves the specific optimization of excited spin coupled wave functions which act as reference functions and are used to introduce correlation corrections directly in the excited state of interest. The variational optimization of such excited wave functions is achieved by using simple orthogonality constraints on the spin coupled orbitals and it preserves all the appealing features of the valence bond method. The applications to the lower lying states of [LiH2]+ and BeH show the advantages and some of the limitations of this new approach. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1388043
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Applications of a variational coupled-electron pair approach to the calculation of intermolecular interaction in the framework of the VB theory: Study of the van der Waals complex He–CH4 (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 6724-6735 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A general nonorthogonal coupled electron pair approach for the evaluation of electron correlation contribution is presented in details. The self-consistent field for molecular interactions wave function is used as reference state for a multistructure valence bond (VB) calculation. The central idea of the method is the optimization of the virtual space of the VB wave function by means of a procedure very close to the independent electron pair approach (IEPA) scheme. All the orbitals employed are expanded in the basis set of their fragment so as to exclude the basis set superposition error (BSSE) in a priori fashion. As an example, the application to the study of the van der Waals complex He–CH4 is reported. The equilibrium geometry of the system occurs at a He–C distance of 3.6 Å , with the He atom pointing to the center of one of the faces of the CH4 molecule, with a well depth of 19 cm−1. The potential energy surface of the He–CH4 complex is used to determine the parameters of a potential model which is employed in close-coupling calculations of integral state-to-state cross sections for rotationally inelastic scattering of methane molecules with helium atoms. The predicted values are compared with the available experimental data. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1287274
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    New basis set superposition error free ab initio MO-VB interaction potential: Molecular-dynamics simulation of water at critical and supercritical conditions (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 3296-3303 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Recently, a controversy has come to light in literature regarding the structure of water in nonambient conditions. Disagreement is evident between the site–site pair correlation functions of water derived from neutron diffraction and those obtained by computer simulations which employ effective pairwise potentials to express the intermolecular interactions. In this paper the SCFMI method (self-consistent field for molecular interaction) followed by nonorthogonal CI (configuration interaction) calculations was used to determine a new water–water interaction potential, which is BSSE (basis set superposition error) free in an a priori fashion. Extensive calculations were performed on water dimer and trimer and a new parametrization of a NCC-like (Niesar–Corongiu–Clementi) potential was accomplished. This was employed in the molecular-dynamics simulation of water. The effect of temperature and density variations was examined. Acceptable agreement between site–site correlation functions derived from neutron diffraction data and from computer simulation was reached. In particular, a weakening of the hydrogen bonded structure was observed on approaching the critical point, which reproduces the experimental behavior. The simulations were performed using the MOTECC (modern techniques in computational chemistry) suite of programs. The present results show the importance of BSSE-free nonorthogonal orbitals in an accurate description of the intermolecular potential of water. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475726
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    An orthogonal approach to determine extremely localised molecular orbitals (2000)
    Springer
    Theoretical chemistry accounts 103 (2000), S. 417-422 
    Details
    ISSN: 1432-2234
    Keywords: Key words: Localised molecular orbitals – Nonorthogonal orbitals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. The introduction of extremely localised molecular orbitals, a current issue in modern physical chemistry, justifies chemical intuition and provides a useful tool towards the description of large molecules. In this paper, a possible strategy to determine these orbitals is proposed. The algorithm implemented has been tested by effecting computations on water, ammonia, benzene and naphthalene by employing different intramolecular partitionings. Ethane and biphenyl have been considered for application of the algorithm to the study of rotational barriers. Our scheme also includes the possibility to compute derivatives with respect to nuclear coordinates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002149900073
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...