computational chemistry - Defining and testing custom made DFT functionals?

What is a good and free software for this endeavor? Any recommended articles on the subject? I want to design dft functionals, trying out different parametrizations and optimizing mixing constants for exchange and correlation contributions for specific data sets. Even add PT2 perturbation energy into the mix if possible.

I am aware of Gaussian's user-defined functional options, but would like to have a bit more control in the parameters and contributions, instead of just 6 parameters.

Answer

Depending on what you're after, you might want to look for programs using libxc, so you can completely define your own functionals.

From the libxc section of the Octopus wiki, these include:

• Abinit – plane-wave code


• APE – an atomic code


• Atomistix ToolKit – numerical orbitals code


• AtomPAW – projector augmented wave functions generator



• BigDFT – wavelet code


• CP2K - A program to perform atomistic and molecular simulations of solid state, liquid, molecular, and biological systems.


• DP – Dielectric Properties, a linear response TDDFT code


• Elk – FP-LAPW code


• ERKALE – a DFT/HF molecular electronic structure code based on Gaussian orbitals


• exciting – FP-LAPW code


• GPAW – grid-based projector-augmented wave method


• JDFTx – plane-wave code designed for Joint Density Functional Theory


• MOLGW - a small, but accurate MBPT code for molecules


• octopus – real-space (TD)DFT code



• Yambo – solid state and molecular physics many-body calculations code

On a more personal note, and this is just my opinion, if you're just arbitrarily mixing functionals, you should really make sure you have a scientific justification for doing this, otherwise you're just generating numbers without basis.