Summary
Dielectric constant describes increased capacitance associated with insulator placed between parallel plates
Insulator responds to an external field by polarizing
Polarization leads to surface charge that offsets imposed field
Charges at infinitely distant boundary have local effect due to this offsetting field
If the system is embedded in a conducting medium, it will respond in a way the eliminates the surface-charge effect
Susceptibility describes linear relation between polarization and external field
- 2nd-derivative property related to fluctuations in polarization
Reaction field method is a simpler and more efficient alternative to the Ewald sum