ABSTRACT
Within the Landau-like approach we study anomalies of elastic moduli at phase transitions in thin films on substrates. We consider the case where, similar to many experimental cases, the first-order transition in free crystal would convert into a second order in the film if the system remained homogeneous. It is shown, however, that apart from its questionable thermodynamic advantages, the homogeneous state of low-symmetry phase may become absolutely unstable which is signaled by changing of sign of its bulk modulus.
Acknowledgments
A. L. is greateful to A. L. Roytburd for stimulating discussions and to B. Spivak for drawing his attention to Ref. Citation[7].