Chapter 6
Conclusion
The comparison of ab initio calculations with results obtained in the long-range
approximation shows that the analytical calculations may be effectively used for
description of the interacting energy, dipole moment, polarizability and first
hyperpolarizability of the considered interacting molecules for R > *10 a.u. So,
we can conclude that analytical calculations for large R are a good support to
ab initio calculations for full description of interaction energy surface and electrical
properties of any pair of interacting molecules. For the range of smaller R, within
the potential well, the exchange-interaction contributions are become to be
significant due to overlapping of electron shells of interacting molecules. The
exchange effects are strong anisotropic and give especially large contributions to the
component of any electrical property determined only by the component of dipole
moment directed along the intermolecular axis. The same situation occurs for
induced dipole moments, dipole polarizabilities, first hyperpolarizability of any
complex and, as we assume, has also to be fulfilled for other higher polarizabilities.
As a result, the following receipt of calculations of electric properties (and energy
surfaces) for molecular complexes is seen. For the values of intermolecular
distances R within the potential well the accurate methods of quantum chemistry
must be used. And for large R, which are usually more then van der Waals radius of
interacting molecules, the analytical methods based on the long-range approximation can be effectively used to change the resource-consuming ab initio calculations.
The use the analytical calculations allows to solve the computational problem
appeared when a fine grid of calculated points for surfaces of any properties is
needed. And the necessity to have a lot of the points (for periphery of a surface the
number of these points tends to infinity) disappears.
© The Author(s) 2017
V.N. Cherepanov et al., Interaction-induced Electric Properties of van der Waals Complexes,
SpringerBriefs in Electrical and Magnetic Properties of Atoms, Molecules, and Clusters,
DOI 10.1007/978-3-319-49032-8_6
103
Conclusion
The comparison of ab initio calculations with results obtained in the long-range
approximation shows that the analytical calculations may be effectively used for
description of the interacting energy, dipole moment, polarizability and first
hyperpolarizability of the considered interacting molecules for R > *10 a.u. So,
we can conclude that analytical calculations for large R are a good support to
ab initio calculations for full description of interaction energy surface and electrical
properties of any pair of interacting molecules. For the range of smaller R, within
the potential well, the exchange-interaction contributions are become to be
significant due to overlapping of electron shells of interacting molecules. The
exchange effects are strong anisotropic and give especially large contributions to the
component of any electrical property determined only by the component of dipole
moment directed along the intermolecular axis. The same situation occurs for
induced dipole moments, dipole polarizabilities, first hyperpolarizability of any
complex and, as we assume, has also to be fulfilled for other higher polarizabilities.
As a result, the following receipt of calculations of electric properties (and energy
surfaces) for molecular complexes is seen. For the values of intermolecular
distances R within the potential well the accurate methods of quantum chemistry
must be used. And for large R, which are usually more then van der Waals radius of
interacting molecules, the analytical methods based on the long-range approximation can be effectively used to change the resource-consuming ab initio calculations.
The use the analytical calculations allows to solve the computational problem
appeared when a fine grid of calculated points for surfaces of any properties is
needed. And the necessity to have a lot of the points (for periphery of a surface the
number of these points tends to infinity) disappears.
© The Author(s) 2017
V.N. Cherepanov et al., Interaction-induced Electric Properties of van der Waals Complexes,
SpringerBriefs in Electrical and Magnetic Properties of Atoms, Molecules, and Clusters,
DOI 10.1007/978-3-319-49032-8_6
103