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qp2/src/README.rst
2020-04-02 16:24:33 +02:00

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The core modules of the QP
==========================
*** How are handled the DFT functionals in QP2 ?
================================================
The Exchange and Correlation energies/potentials can be accessed by the following providers
energy_x
energy_c
potential_x_alpha_ao
potential_c_alpha_ao
potential_x_beta_ao
potential_c_beta_ao
These providers are automatically linked to the providers of the actual exchange/correlation energies of a given functional
through the character keywords
"exchange_functional"
"correlation_functional"
All the providers for the available functionals are in the folder "functionals", with one file "my_functional.irp.f" per functional.
Ex : if "exchange_functional" == "sr_pbe", then energy_x will contain the exchange correlation functional defined in "functiona/sr_pbe.irp.f", which corresponds to the short-range PBE functional (at the value mu_erf for the range separation parameter)
*** How to add a new functional in QP2
======================================
Creating a new functional and propagating it through the whole QP2 programs is easy as all dependencies are handled by a script.
To do so, let us assume that the name of your functional is "my_func".
Then you just have to create the file "my_func.irp.f" in the folder "functional" which shoud contain
+) if you're adding an exchange functional, then create the provider "energy_x_my_func"
+) if you're adding a correlation functional, create the provider "energy_c_my_func"
+) if you want to add the echange potentials, create the providers "potential_x_alpha_ao_my_func", "potential_x_beta_ao_my_func" which are the exchange potentials on the AO basis for the alpha/beta electrons
+) if you want to add the correlation potentials, create the providers "potential_c_alpha_ao_my_func", "potential_c_beta_ao_my_func" which are the correlation potentials on the AO basis for the alpha/beta electrons
That's all :)
Then, when running whatever DFT calculation or accessing/using the providers:
energy_x
energy_c
potential_x_alpha_ao
potential_c_alpha_ao
potential_x_beta_ao
potential_c_beta_ao
if exchange_functional = mu_func, then you will automatically have access to what you need, such as kohn sham orbital optimization and so on ...