Chapter 5
Molecular Theory of Local Field
Abstract In applying the microscopic SFG theory to actual interfaces, polarization
properties of condensed dielectric media have to be properly described. These
properties in uniform bulk media are often described with a phenomenological
model, though the detailed microscopic treatment becomes indispensable at inhomogeneous interfaces. This chapter summarizes the molecular theory of polarization
properties and offer a general scheme to calculate them by molecular simulation.
These properties can be determined in principle from molecular properties and their
interactions. This theory is of general significance to light-matter interactions, and
also an integral part in the computational analysis of SFG.
Keywords Local field correction factor · Effective polarizability · Interfacial
dielectric constant
The preceding chapter has given two representations of the second-order nonlinear
susceptibility χ (2) , using the polarizability α and the dipole moment μ of the
interface system. In this chapter, we argue how the polarizability and dipole
moment of the interface system are described from microscopic configuration of
molecules. In the following discussion, the polarizability and dipole moment of
the whole interface system are denoted with the capital letters by A and M,
respectively, to distinguish them from molecular properties. In the condensed phase,
the polarization properties such as A and M are affected by electrostatic interactions
among constituent molecules. The electrostatic intermolecular interactions mutually
polarize the constituent molecules, and consequently, the polarizability or dipole
moment of the whole system do not become the simple sum of polarizability or
dipole moment of non-interacting molecules. The reliable description of χ (2) should
take account of this effect of polarization coupling.
The coupling of polarizations is the origin of local field effect in a dielectric
medium, i.e. the local electric field at a molecule in the condensed phase is
influenced by the electrostatic interactions from neighboring molecules and thereby
deviates from the external field [3]. In the classical theory of dielectrics, the local
field effect is often treated by the simple Lorentz model or its analogues for a bulk
© Springer Nature Singapore Pte Ltd. 2018
A. Morita, Theory of Sum Frequency Generation Spectroscopy,
Lecture Notes in Chemistry 97, https://doi.org/10.1007/978-981-13-1607-4_5
105
Molecular Theory of Local Field
Abstract In applying the microscopic SFG theory to actual interfaces, polarization
properties of condensed dielectric media have to be properly described. These
properties in uniform bulk media are often described with a phenomenological
model, though the detailed microscopic treatment becomes indispensable at inhomogeneous interfaces. This chapter summarizes the molecular theory of polarization
properties and offer a general scheme to calculate them by molecular simulation.
These properties can be determined in principle from molecular properties and their
interactions. This theory is of general significance to light-matter interactions, and
also an integral part in the computational analysis of SFG.
Keywords Local field correction factor · Effective polarizability · Interfacial
dielectric constant
The preceding chapter has given two representations of the second-order nonlinear
susceptibility χ (2) , using the polarizability α and the dipole moment μ of the
interface system. In this chapter, we argue how the polarizability and dipole
moment of the interface system are described from microscopic configuration of
molecules. In the following discussion, the polarizability and dipole moment of
the whole interface system are denoted with the capital letters by A and M,
respectively, to distinguish them from molecular properties. In the condensed phase,
the polarization properties such as A and M are affected by electrostatic interactions
among constituent molecules. The electrostatic intermolecular interactions mutually
polarize the constituent molecules, and consequently, the polarizability or dipole
moment of the whole system do not become the simple sum of polarizability or
dipole moment of non-interacting molecules. The reliable description of χ (2) should
take account of this effect of polarization coupling.
The coupling of polarizations is the origin of local field effect in a dielectric
medium, i.e. the local electric field at a molecule in the condensed phase is
influenced by the electrostatic interactions from neighboring molecules and thereby
deviates from the external field [3]. In the classical theory of dielectrics, the local
field effect is often treated by the simple Lorentz model or its analogues for a bulk
© Springer Nature Singapore Pte Ltd. 2018
A. Morita, Theory of Sum Frequency Generation Spectroscopy,
Lecture Notes in Chemistry 97, https://doi.org/10.1007/978-981-13-1607-4_5
105