Let us compare a system of \( N \)-independent electrons with pseudo-independent electrons described by the mean-field Hartree-Fock model. Fill the table below. Use Koopmans theorem when appropriate. Define any notations you use, i.e.: \[ \begin{array}{r} h_{i} \equiv h\left(x_{i}\right)=-\frac{1}{2} \nabla_{i}^{2}-\sum_{A} \frac{Z_{A}}{\left|R_{a}-r_{i}\right|} \\ v_{i j} \equiv v\left(x_{i}, x_{j}\right)=\frac{1}{\left|r_{i}-r_{j}\right|} \\ \Phi_{k}=\mid \phi_{1} \phi_{2} \ldots \not \not_{K} \ldots \phi_{N}> \\ \Phi_{i}^{a}=\mid \phi_{1} \phi_{2} \ldots\left\{\not X\left\langle\phi_{a}\right\} \ldots \phi_{N}>\right. \end{array} \] \begin{tabular}{||l|l|l||} \hline & Independent electrons & Pseudo-independent electrons \\ \hline Hamiltonian & \( H=\sum_{i=1}^{N} \hat{h}_{i} \) & \( H=\sum_{i=1}^{N} \hat{h}_{i}+\frac{1}{2} \sum_{i j=1}^{N} v_{i j} \) \\ \hline Wfn \( \left|\Phi_{0}\right\rangle= \) & \( \left|\phi_{1} \phi_{2} \ldots \phi_{N}\right\rangle \) & \( \left|\phi_{1} \phi_{2} \ldots \phi_{N}\right\rangle \) \\ \hline\( \phi_{i} \) are solutions of: & & \\ \hline Total energy is: & & \\ \hline \begin{tabular}{l} Energy required to remove \\ electron from \( \phi_{k} \) \end{tabular} & & \\ \hline \begin{tabular}{l} Energy for attaching \\ electron to \( \phi_{a} \notin \Phi_{0} \) \end{tabular} & & \\ \hline \begin{tabular}{l} Energy difference between \\ \( \Phi_{k} \) and \( \Phi_{j} \) \end{tabular} & & \\ \hline \begin{tabular}{l} Energy difference between \\ \( \Phi_{0} \) and \( \Phi_{i}^{a} \) \end{tabular} & & \\ \hline \end{tabular}
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- **Independent electrons**: The Hamiltonian is given by \( H = \sum_{i=1}^{N} \hat{h}_{i} \). - **Pseudo-independent electrons**: The Hamiltonian is \( H = \sum_{i=1}^{N} \hat{h}_{i} + \frac{1}{2} \sum_{i j=1}^{N} v_{i j} \). Show more…
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1. In this problem we will examine the physical significance of the eigenvalue $\in$ in Equation $8.20$. The quantity $\epsilon$ is called the orbital energy. Using Equation $8.19$ for $\hat{H}_{1}^{\text {eff }}\left(\mathbf{r}_{1}\right)$, multiply Equation $8.20$ from the left by $\phi^{*}\left(\mathbf{r}_{1}\right)$ and integrate to obtain $$ \varepsilon_{1}=I_{1}+J_{12} $$ where $I_{1}$ and $J_{12}$ are defined in the previous problem. Show that the total energy of a helium atom $E=I_{1}+I_{2}+J_{12}$ is not the sum of its orbital energies. In fact, show that $$ \epsilon_{1}=E-I_{2} $$ But according to the definition of $I_{2}$ in Problem 8-10, $I_{2}$ is the energy of a helium ion, calculated with the helium Hartree-Fock orbital $\phi(r)$. Thus, Equation 1 suggests that the orbital energy $\epsilon_{1}$ is an approximation to the ionization energy of a helium atom or that, $$ \text { IE } \approx-\epsilon_{1} \quad \text { (Koopmans' approximation) } $$ Even within the Hartree-Fock approximation, Koopmans' approximation is based upon the approximation that the same orbitals can be used to calculate the energy of the neutral atom and the energy of the ion. The value of $-\epsilon_{1}$ obtained by Clementi (see Table $8.2$ ) is $0.91796 E_{b}$, compared with the experimental value of $0.904 E_{h}$.
(a) Five free electrons exist in a three-dimensional infinite potential well with all three widths equal to $a=12 \AA$. Determine the Fermi energy level at $T=0 \mathrm{~K} .(b)$ Repeat part $(a)$ for 13 electrons.
The wave function for the quantum harmonic oscillator in the ground state is given by ψ₀(x) = C₀e^{-mωx²/2ħ}. Find the normalization constant C₀. b) Calculate <x>, <x²>, and Δx = (<x²> - <x>²)¹/² for a quantum oscillator in its ground state. Hint: Use the integral formula.
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