Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Phenomenological theory of phase transitions in highly piezoelectric
  perovskites   Recently discovered fine structure of the morphotropic phase boundaries in
highly piezoelectric mixture compounds PZT, PMN-PT, and PZN-PT demonstrates the
importance of highly non-linear interactions in these systems. We show that an
adequate Landau-type description of the ferroelectric phase transitions in
these compounds is achieved by the use of a twelfth-order expansion of the
Landau potential in terms of the phenomenological order parameter.
Group-theoretical and catastrophe-theory methods are used in constructing the
appropriate Landau potential. A complete phase diagram is calculated in
phenomenological parameter space. The theory describes both PZT and PZN-PT
types of phase diagrams, including the newly found monoclinic and orthorhombic
phases. Anomalously large piezoelectric coefficients are predicted in the
vicinity of the phase transition lines.

7
The categories of this paper are: hep-th
17
The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
21
The categories of this paper are: adap-org
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph