Cluster Calculations of Nuclear Magnetic Resonance Chemical Shielding in Alloy Piezoelectric Solids

The local atomic structure of high performance piezoelectric materials is currently being investigated computationally. These materials are expected to play an important role in the next generation of sensors and actuators, used for example, in aircraft for active vibration and noise control. Many sensors and actuators are composed of piezoelectric materials, since they can transform mechanical to electrical energy (and vice versa). The goal of this study is to understand how the local atomic structure is related to piezoelectric properties. For example, B-site alloys with the perovskite structure ABO3 such as Pb(Zr,Ti)O3 and Pb(Mg,Nb)O3 have extremely different piezoelectric characteristics. Nuclear magnetic resonance (NMR) has been shown to be a sensitive experimental probe of the local structure, but it is difficult to interpret the measurements without theoretical modeling. This study uses first-principle quantum mechanical calculations to determine the NMR chemical shielding tensor in order to replicate the NMR spectrum. Recent progress in performing these calculations will be discussed. The methodology was first tested on simple systems, MgO and CaO, which are well understood. Preliminary results for PbTiO3 are presented.