During the past decade the theoretical physics community has learned how
to evaluate accurately polarizabilities and susceptibilities for
many-electron systems such as atoms, solids, and liquids. The most
accurate numerical technique employs a method often called the
Time-Dependent Local Density Approximation, which is abbreviated TDLDA.
The present volume is a review of recent research on the theory of po-
larizabilities and susceptibilities. Both authors have been doing these
cal- culations. However, this review surveys the entire field,
summarizing the research of many contributors. The application of an
external field, either ac or de, will induce a dipole moment which can
be calculated and compared with experiment. For mod- erately strong
fields, both linear and nonlinear processes contribute to the moment. We
cover topics such as polarizability, hyperpolarizability, pho-
toionization, phonons, and piezoelectricity. Density functional theory
in the Local Density Approximation (LDA) has been shown to be a very
accurate method for calculating ground state prop- erties of electronic
system. For static external fields, the induced moments are properties
of the ground state. Then the calculation of the polarizability - is
very accurate. For ac fields, the moment is not part of the ground
state. However, the TDLDA methods are still very accurate.