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What does Hartree-Fock do?
In computational physics and chemistry, the Hartree–Fock (HF) method is a method of approximation for the determination of the wave function and the energy of a quantum many-body system in a stationary state.
How does the Hartree-Fock method work?
The Hartree-Fock (HF) method is a variational method that provides the wave function of a many-body system assumed to be in the form of a Slater determinant for fermions and of a product wave function for bosons.
What is a Hartree Orbital?
Hartree-Fock theory is fundamental to much of electronic structure theory. It is the basis of molecular orbital (MO) theory, which posits that each electron’s motion can be described by a single-particle function (orbital) which does not depend explicitly on the instantaneous motions of the other electrons.
What is Hartree term?
The third term, or Hartree term, is the simply electrostatic potential arising from the charge distribution of electrons. As written, the term includes an unphysical self-interaction of electrons when. . This term is cancelled in the fourth, or exchange term.
How is Hartree potential calculated?
The Hartree potential is defined as the electrostatic potential from the electron charge density and must be calculated from the Poisson equation: ∇2VH[n](r)=−4πn(r). ∇ 2 V H [ n ] ( r ) = − 4 π n ( r ) .
What is correlation effect?
A correlation identifies variables and looks for a relationship between them. An experiment tests the effect that an independent variable has upon a dependent variable but a correlation looks for a relationship between two variables.
Why is correlation energy important?
Electronic correlation is the interaction between electrons in the electronic structure of a quantum system. The correlation energy is a measure of how much the movement of one electron is influenced by the presence of all other electrons.
What kind of orbitals are used in Hartree Fock?
Typically, in modern Hartree–Fock calculations, the one-electron wave functions are approximated by a linear combination of atomic orbitals. These atomic orbitals are called Slater-type orbitals.
How is energy given in Hartree Fock theory?
In Hartree-Fock (HF) theory the energy of a system is given as a sum of five components: The nuclear-nuclear repulsion E NN describes the electrostatic repulsion between the nuclei and is independent of the electron coordinates.
Which is the first step in Hartree Fock calculations?
After reading in the geometry of the system and determining its symmetry properties, the actual first step of Hartree-Fock calculations consists in choosing a basis set in which the electronic wavefunction can be expanded. This is done in link 301 of the program, usually by calling a predefined set of basis functions from a library.
How is the wavefunction of HF theory described?
The molecular electronic wavefunction in HF theory is based on the LCAO (=linear combination of atomic orbitals) scheme describing each molecular orbital (holding one electron) as a linear combination of basis functions (usually located at the nuclear center):