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https://github.com/LCPQ/quantum_package
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47 lines
1.2 KiB
ReStructuredText
47 lines
1.2 KiB
ReStructuredText
.. _fci:
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.. program:: fci
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.. default-role:: option
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===
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FCI
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===
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Selected Full Configuration Interaction.
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The program start with a single determinant, or with the wave function in the |EZFIO| database if :option:`determinants read_wf` is |true|. Then, it will iteratively:
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* Select the most important determinants from the external space and add them to the
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internal space
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* If :option:`determinants s2_eig` is |true|, add all the necessary
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determinants to allow the eigenstates of |H| to be eigenstates of |S^2|
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* Diagonalize |H| in the enlarged internal space
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* Compute (stochastically) the second-order perturbative contribution to the energy
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* Extrapolate the variational energy by fitting
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:math:`E=E_\text{FCI} - \alpha\, E_\text{PT2}`
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The number of selected determinants at each iteration will be such that the
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size of the wave function will double at every iteration.
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By default, the program will stop when more than one million determinants have
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been selected, or when the |PT2| energy is below :math:`10^{-4}`.
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EZFIO parameters
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----------------
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.. option:: energy
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Calculated Selected |FCI| energy
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.. option:: energy_pt2
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Calculated |FCI| energy + |PT2|
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