We introduce "TALK 2: Exchange-Correlation for Band-Structures and Device".
In this talk, we discuss what exchange and correlation (XC) is in the context of density functional theory.
The various types of XC functionals is described including the local density and generalised gradient approximations, meta-GGAs, hybrid functionals and DFT+U. Examples of their use in CASTEP is given looking at a number of properties including band gap and their computational cost. Future XC functionality in Castep is presented.