Ferroelectric phase transitions in nano-scale chemically ordered PbSc0.5Nb0.5O3 using a first-principles model hamiltonian

Effects of chemical order, disorder, short range order, and anti-phase boundaries on phase transitions and dielectric properties of PbSc1/2Nb1/2O3 are studied through molecular dynamics simulations of a FP model. Simulations of large systems are required to capture these effects, and we present an efficient reciprocal space method, based on fast Fourier transforms, for calculating long-range interactions and inhomogeneous strain. Calculations for random or partially disordered systems yield significant increases in T = 0 K dielectric response, and broadening of the ferroelectric phase transition. Coupling between random fields caused by chemical disorder and the inhomogeneous strain (acoustic modes) affects the dynamics of soft modes in chemically nano-structured configurations.