====== How can I generate a new basis set? ======

We have different options available to generate basis sets within CP2K.
However, all of them also require a large part of manual invention.
There are no black box schemes.

===== Method 1: =====

Optimize the exponents of a Gaussian basis with the atomic code for a given reference state (see [[https://github.com/search?q=repo%3Acp2k%2Fcp2k+filename%3ARu*.inp+path%3A%2Ftests%2FATOM%2Fregtest-2&type=Code|tests/ATOM/regtest-2/Ru*.inp]]). You have to choose the number of Gaussians per $l$ quantum number, atomic state, ...) Calculate the contraction coefficients and generate additional functions using a recipe from quantum chemistry.

You might want to add polarization functions that are not available through atomic calculations.

===== Method 2: =====
Just like Method 1 but calculate the contractions from a atomic response calculation. ([[src>tests/ATOM/regtest-2/Ru_basis.inp]])


===== Method 3: =====
MOLOPT basis sets. This requires extensive calculations on test molecules. you can see an example in [[src>tests/QS/regtest-optbas]]