Fig. 14: Sketch of the i-th Ti-center of structure A, along with its enclosing oxygen cage and the two vectors \({\tilde{{{{\bf{P}}}}}}_{i}(A)\) and \({\tilde{Q}}_{i}^{an}(A)\) associated with it.
From: Thermodynamics and dielectric response of BaTiO3 by data-driven modeling
The final CV is computed as a scalar product of these quantities after first summing over all Ti-centers.
