Dielectric, piezoelectric and magnetoelectric properties via first-principles calculations at constant electric displacement
Massimiliano Stengel
Finite-field calculations in periodic insulators are technically and conceptually challenging, due to fundamental problems in defining the polarization in extended solids. While significant progress has been made recently with the establishment of techniques to fix the electric field E or the macroscopic polarization P in first-principles calculations, both methods lack the ease of use and conceptual clarity of standard zero-field calculations. In this talk I will present a new formalism in which the electric displacement D, rather than E or P, is the fundamental electrical variable. Fixing D has the intuitive interpretation of imposing open-circuit electrical boundary conditions, which is particularly useful in studying ferroelectric systems. Furthermore, the analogy to open-circuit capacitors suggests an appealing reformulation in terms of free charges and potentials, which dramatically simplifies the treatment of stresses and strains. I will discuss applications of this method to the calculation of the nonlinear dielectric and piezoelectric properties of PbTiO3, to the calculation of interfacial depolarizing effects in ferroelectric capacitors, and to the calculation of interfacial magnetoelectric effects mediated by spin-polarized carriers.
