add DOS acronym

docs/4_sommerfeld_model_solutions.md

@@ -255,3 +255,4 @@ $$
 C_v(T) = \frac{\partial E}{\partial T} = \frac{3L^2k_B^3T^2}{\pi c^2}
 $$
 
+*[DOS]: Density of states
\ No newline at end of file

docs/6_bonds_and_spectra.md

@@ -666,3 +666,5 @@ Make the masses of every even atom different from the masses of every odd atom.
 #### Question 4.
 Now make the masses of even and odd atoms equivalent again. Furthermore, make the spring constants of every even spring different from the odd spring.
 Compute the eigenfrequencies of this atomic chain and plot a histogram.
+
+*[DOS]: Density of states

docs/7_tight_binding.md

@@ -459,3 +459,5 @@ Solve the Schrödinger equation to find the dispersion relation $E(k)$.
 Calculate the effective mass $m^*$.
 #### Question 4.
 Sketch the effective mass as a function of $k$ for the cases $t=2t'$, $t=4t'$, and $t=10t'$.
+
+*[DOS]: Density of states

docs/8_many_atoms.md

@@ -338,3 +338,5 @@ In general, the eigenvalue problem above cannot be solved analytically, and can
 
 #### Question 5.
 What will happen to the periodicity of the band structure if $κ_ 1 = κ_ 2 = κ_3$?
+
+*[DOS]: Density of states