Welcome to XCFun documentation

XCFun is a library of exchange-correlation (XC) functionals to be used in density-functional theory (DFT) codes. XCFun follows a unique implementation strategy which enables the computation of derivatives of the XC functional kernel up to arbitrary order. It does so by relying on forward-mode automatic differentiation.

Given a new XC functional kernel, its implementation with all its derivatives only requires to write code for the undifferentiated kernel. This implementation strategy is very powerful and allows:

  1. Faster implementation of new functionals: you write the kernel, the compiler does the rest.

  2. Introduction of new variables, for example current densities, in the parametrization of new or existing XC kernels.

  3. Testing for numerical stability of XC kernels, using arbitrary precision arithmetic libraries.


Indices and tables