Manifestations of structural phase transition in ab initio molecular dynamics of (C 3 N 2 H 5 ) 2 SbF 5 crystal

Abstract Structural and electronic properties of the ferroelastic crystal (C 3 N 2 H 5 ) 2 SbF 5 characterized by first-order phase transition were studied by ab initio methods in the framework of density functional theory. The molecular dynamics calculations were performed at different temperatures in the range T C - 70 ÷ T C  + 70° containing the phase transition point T C . In this approach, atomic scale (microscopic) manifestations of this transition were obtained. The quasi continuous temperature changes of some microscopic properties in the relatively wide temperature range around T C were observed in spite of sharp experimental temperature dependences of several macroscopic properties of (C 3 N 2 H 5 ) 2 SbF 5 near the first order phase transition point T C (latent heat flow, dielectric permittivity). The latter peculiarities may be regarded as the microscopic precursors of the first order phase transition in (C 3 N 2 H 5 ) 2 SbF 5 . Different specific kinetic energies (energy per one atom) for five constituting chemical elements (C, N, H, Sb and F) of the crystal have been detected for the first time, indicating for different abilities of the interatomic energy exchange.