ABSTRACT
Time-Independent and Periodic Time-Dependent Potentials ...................... 73 6.3 Formal Foundations of Density Functional Theory for
Time-Dependent Electric and Magnetic Fields ........................................... 74 6.4 Practical Schemes for the Calculation of Density and
Current Density Variables in TDDFT ......................................................... 77 6.5 Linear Response within TDDFT ................................................................. 79 6.6 Concluding Remarks.................................................................................... 80 Acknowledgments................................................................................................... 80 References ............................................................................................................... 81
The study of behavior of many-electron systems such as atoms, molecules, and solids under the action of time-dependent (TD) external fields, which includes interaction with radiation, has been an important area of research. In the linear response regime, where one considers the external field to cause a small perturbation to the initial ground state of the system, one can obtain many important physical quantities such as polarizabilities, dielectric functions, excitation energies, photoabsorption spectra, van der Waals coefficients, etc. In many situations, for example, in the case of interaction of many-electron systems with strong laser field, however, it is necessary to go beyond linear response for investigation of the properties. Since a full theoretical description based on accurate solution of TD Schrodinger equation is not yet within the reach of computational capabilities, new methods which can efficiently handle the TD many-electron correlations need to be explored, and time-dependent density functional theory (TDDFT) is one such valuable approach.
