The use of k‐q functions is introduced into the Landau theory of second order phase transitions. The expansion of an arbitrary density function in a crystal is given in terms of basis functions of irreducible representations of a space group which are linear combinations of k‐q functions. This leads to a new condition on the irreducible representations which can be associated with second order phase transitions.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics