I try to find the elastic constants of LiTaO3 from online databases. I did find a page that lists them https://www.roditi.com/SingleCrystal/Lithium-Tantalate/LiTaO3-Properties.html
As I know, the elastic constants are defined with respect to a predefined coordination system. However, the page gives nothing about the coordination system. So is there a convention of the predefined coordination system for defining the elastic constants or how should I know the coordination system corresponding to the experimental elastic constants ?