Cluster Calculations of Nuclear Magnetic Resonance Chemical Shielding in Piezoelectric Solid Alloys

High performance piezoelectric 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. Piezoelectric materials 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. I show here that first-principles quantum mechanical calculations of chemical shielding can accurately predict oxygen NMR isotropic chemical shifts δiso(O) in Pb based perovskites. Calculations of δiso(O) are presented for the end point compounds PbTiO3 and PbZrO3, and for the 50/50 alloy Pb(Zr1/2Ti1/2)O3. The δiso(O) values are relate to variations in the Ti-O and Zr-O bond lengths and used to interpret recent experimental measurements.