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Fock Matrix

Tim Strang

The Fock matrix is a mathematical object which represents the Fock operator via its action on a finite single-particle orbital basis set. Though not a true Hamiltonian, the Fock operator behaves as an effective single-particle Hamiltonian operator which takes as inputs a set of occupied orbitals. Two-electron effects are then computed as an average field over all other occupied orbitals.

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Free Energy

Yue Ma

For a thermodynamic process, the “lost” internal energy (the sum of kinetic and potential energy of the system) which can be converted to external work is described by the term free energy, also known as the thermodynamic free energy, which is a state function.

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Full Configuration Interaction

Ryan Choi

Full configuration interaction (FCI) is a variational method that improves upon Hartree-Fock. It is numerically exact, and is therefore used to benchmark other methods; however, it is also computationally expensive, limited to about sixteen electrons in sixteen orbitals.

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Fundamental Band Gap

Michelle Bishka

The fundamental band gap is the energy difference between the highest energy state of the valence band and the lowest energy state of the conduction band. The valence band is the furthest band from the atomic nucleus that is still occupied by electrons, while the conduction band is a higher-energy range of electronic states where electrons move freely.

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