From 9330916027427583ffd31964278850a113cb4773 Mon Sep 17 00:00:00 2001
From: Umut Kalkan <umut.kalkan@live.nl>
Date: Tue, 6 Apr 2021 18:23:27 +0000
Subject: [PATCH] Update 11_nearly_free_electron_model.md

bold, italic text fix
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 src/11_nearly_free_electron_model.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/11_nearly_free_electron_model.md b/src/11_nearly_free_electron_model.md
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@@ -93,7 +93,7 @@ In this figure, the orange curves represent the nearly-free electron dispersion,
 
 ### Analyzing the avoided crossings
 
-*Remark: An avoided crossing is an important concept in quantum mechanics that can be analyzed using **perturbation theory**. You will only learn this theory later in QMIII, so we will need to postulate some important facts here.*
+*Remark: An avoided crossing is an important concept in quantum mechanics that can be analyzed using ***perturbation theory***. You will only learn this theory later in QMIII, so we will need to postulate some important facts here.*
 
 To analyze what happens near the crossings, we first neglect the lattice potential and consider the free-electron dispersion near the crossing at $k=\pi/a$ in 1D. Near this crossing, we see that two copies of the dispersion come together (one copy centered at $k=0$, the other at $k=2\pi/a$). We call the corresponding plane-wave eigenfunctions $|k\rangle$ and $|k'\rangle =|k-2\pi/a\rangle$. We now express the wavefunction near this crossing as a linear superposition $|\psi\rangle = \alpha |k\rangle + \beta |k'\rangle$. Note that this wave function is very similar to that used in the LCAO model, except there we used linear combinations of the orbitals $|1\rangle$ and $|2\rangle$ instead of the plane waves $|k\rangle$ and $|k'\rangle$.
 
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