Ab initio theory of metal-insulator interfaces in a finite electric field

We present a technique for calculating the dielectric response of periodic metal-insulator heterostructures. This scheme allows the fully first-principles calculation of the microscopic properties of thin-film capacitors at finite bias potential. The method can be readily applied to pure insulators, where it provides an appealing alternative to conventional finite-field techniques based on the Berry-phase formalism. We demonstrate the effectiveness of our method by performing comprehensive numerical tests on a model Ag/MgO/Ag heterostructure.