Done with IID
This commit is contained in:
parent
d964d2cd01
commit
a63579aa37
@ -471,16 +471,13 @@ with the corresponding matrix elements
|
||||
h_i & = \mel{\phi_i}{\Hat{h}}{\phi_i},
|
||||
&
|
||||
f_i & = \mel{\phi_i}{\Hat{f}}{\phi_i}.
|
||||
%J_{ij} & = \mel{\phi_i}{\Hat{J}_j}{\phi_i},
|
||||
%&
|
||||
%K_{ij} & = \mel{\phi_i}{\Hat{K}_j}{\phi_i}.
|
||||
\end{align}
|
||||
The optimal HF wave function is identified by using the variational principle to minimise the HF energy.
|
||||
For any system with more than one electron, the resulting Slater determinant is not an eigenfunction of the exact Hamiltonian $\hH$.
|
||||
However, it is by definition an eigenfunction of the approximate many-electron HF Hamiltonian constructed
|
||||
from the one-electron Fock operators as
|
||||
\begin{equation}\label{eq:HFHamiltonian}
|
||||
\hH_{\text{HF}} = \sum_{i} f(\vb{x}_i).
|
||||
\hH_{\text{HF}} = \sum_{i}^{N} f(\vb{x}_i).
|
||||
\end{equation}
|
||||
From hereon, $i$ and $j$ denote occupied orbitals, $a$ and $b$ denote unoccupied (or virtual) orbitals, while $p$, $q$, $r$, and $s$ denote arbitrary orbitals.
|
||||
|
||||
@ -488,12 +485,12 @@ From hereon, $i$ and $j$ denote occupied orbitals, $a$ and $b$ denote unoccupied
|
||||
In the most flexible variant of real HF theory (generalised HF) the one-electron orbitals can be complex-valued
|
||||
and contain a mixture of spin-up and spin-down components.\cite{Mayer_1993,Jimenez-Hoyos_2011}
|
||||
However, the application of HF with some level of constraint on the orbital structure is far more common.
|
||||
Forcing the spatial part of the orbitals to be the same for spin-up and spin-down electrons leads to restricted HF (RHF) theory,
|
||||
Forcing the spatial part of the orbitals to be the same for spin-up and spin-down electrons leads to restricted HF (RHF) method,
|
||||
while allowing different orbitals for different spins leads to the so-called unrestricted HF (UHF) approach.\cite{StuberPaldus}
|
||||
The advantage of the UHF approximation is its ability to correctly describe strongly correlated systems,
|
||||
such as antiferromagnetic phases\cite{Slater_1951} or the dissociation of the hydrogen dimer,\cite{Coulson_1949}
|
||||
such as antiferromagnetic phases\cite{Slater_1951} or the dissociation of the hydrogen dimer.\cite{Coulson_1949}
|
||||
However, by allowing different orbitals for different spins, the UHF is no longer required to be an eigenfunction of
|
||||
the total spin $\hat{\mathcal{S}}^2$ operator, leading to ``spin-contamination'' in the wave function.
|
||||
the total spin operator $\hat{\mathcal{S}}^2$, leading to ``spin-contamination'' in the wave function.
|
||||
|
||||
%================================================================%
|
||||
\subsection{Hartree--Fock in the Hubbard Dimer}
|
||||
|
Loading…
Reference in New Issue
Block a user