Theory of ferroelectrics: a vision for the next decade and beyond

Abstract

In the last ten years significant advances have been made in our understanding and ability to compute and predict properties of ferroelectrics and piezoelectrics using fundamental physics. Phase diagrams, electromechanical and elastic properties, and effects of defects and surfaces are now amenable to computation. Most importantly, new techniques have been developed, and new understanding of the meaning of polarization in dielectrics has been developed. Prospects for the future are discussed. Nb23 O 3 -PbTiO 3 ) which will revolutionize fields ranging from sonar and hydrophones to medical ultrasonic imaging [2]. The current state of the field, as will be discussed below, is that we now can compute all of the parameters related to electromechanical coupling, particularly the piezoelectric constants, for pure, ordered, single crystal phases [3,4].

The role of oxygen vacancy in the photoluminescence property at room temperature of the CaTiO3

“…Consequently, this alteration results in the structural order-disorder. Studies on intermediate levels 5 and the order-disorder 43 showed a decrease in the optical band gap according to the structural organization. For the decrease in the optical band gap, three forms of displacement of the VB and CB can be proposed: ͑1͒ an increase in the VB energy and a decrease in the CB energy; ͑2͒ the VB energy remains constant and the CB energy decreases; and ͑3͒ an increase in the VB and CB energy remains constant.…”

Theory of structural response to macroscopic electric fields in ferroelectric systems

“…This follows the spirit of a view of PZN-PT and PMN-PT as large-strain PbTiO 3 -based systems that have been chemically "engineered" to make them marginally stable in the rhombohedral phase. 43 We do something very similar, but using a theoretical manipulation that avoids the unnecessary complexities of the real alloy systems.…”

First principles studies of the born effective charges and electronic dielectric tensors for the relaxor PMN (PbMg1/3Nb2/3O3)

“…PMN exhibits frequency dependent dielectric dispersion characteristic of relaxors and has a large, broad peak at around room temperature [1]. Relaxors are disordered over various length scales, and a multiscale approach involving a combination of various techniques including quantum mechanical, atomistic and continuum approaches [2][3][4] is required. The disorder in PMN gives rise to anomalies in nearly all observed properties including diffuse scattering, dynamical properties and the important applications coupled with their rich physics have resulted in extensive theoretical and experimental studies.…”

“…These can be used to derive interatomic potentials [2][3][4] and effective Hamiltonians which in turn can be employed to study the disordered solid solution PMN-PT over larger length and time scales. Our calculations reveal that ordered PMN supercells are ferroelectric.…”