Here are my constants:
Well width: a = 2b = 1 Angstrom
Well Depth: \(V_0\) = 250 eV
Well Spacing (from one center to another): c = 1.75 Angstroms (chosen because it causes essentially no difference in E1, but a very large difference in E3)
E1:
E1 = -226 eV , k = 2.51 Angstroms^(-1) , \(\kappa\) = 7.7 Angstroms^(-1)
D = 1.26 Angstroms^(-1/2), B = 0.39 Angstroms^(-1/2)
E3:
E3 = -50 eV , k = 7.24 Angstroms^(-1) , \(\kappa\) = 3.62 Angstroms^(-1)
D = 1.14 Angstroms^(-1/2), B = -1.01 Angstroms^(-1/2)
\( E_q^1 = -226 + 0.46cos(1.75q) \)
\( E_q^3 = -50 + 32cos(1.75q) \)
Here are the steps to get here and general equations for all states, in case I got anything wrong:
Following from previous discussions we have
\( E_q = E_0 + 2cos(qc)I_{11}^m \)
\( I_{11}^m = < \phi_0 (x) | V (x-c) | \phi_0 (x-c)> \)
\( < \phi_0 (x) | V (x-c) | \phi_0 (x-c)> = \int_{c-b}^{c+b} \phi_0^* (x) V_0 (x-c) \phi_0 (x-c) dx \)
\( = V_0 \int_{c-b}^{c+b} \phi_0^* (x) \phi_0 (x-c) dx \)
\( \phi_0(x) \) between c-b and c+b is the exponentially falling tail of the wave function centralized at x = 0, and is the same for even and odd functions.
\(\phi_0 (x-c)\) between c-b and c+b is the sinusoidal wave function centered at x=c, and varies from even to odd.
\( = V_0 \int_{c-b}^{c+b} e^{- \kappa x} \phi_0 (x-c) dx \)
odd \( = V_0 D \int_{c-b}^{c+b} e^{- \kappa x} sin(k(x-c)) dx \)
even \( = V_0 D \int_{c-b}^{c+b} e^{- \kappa x} cos(\kappa(x-c)) dx \)
odd \( \frac{V_0 D A e^{-\kappa c}}{k^2 + \kappa^2} [ k(e^{2b\kappa} - 1) cos(bk) - \kappa(e^{2b\kappa} + 1) sin(bk) ] \)
even \( \frac{V_0 D B e^{-\kappa c}}{k^2 + \kappa^2} [ \kappa(e^{2b\kappa} - 1) cos(bk) + k(e^{2b\kappa} + 1) sin(bk) ] \)
odd \( E_q = E_0 + \frac{V_0 D A e^{-\kappa c} cos(qc)}{k^2 + \kappa^2} [ k(e^{2b\kappa} - 1) cos(bk) - \kappa(e^{2b\kappa} + 1) sin(bk) ] \)
even \( E_q = E_0 + \frac{V_0 D B e^{-\kappa c} cos(qc)}{k^2 + \kappa^2} [ \kappa(e^{2b\kappa} - 1) cos(bk) + k(e^{2b\kappa} + 1) sin(bk) ] \)
\( E_q^1 = -226 + 327,050e^{-7.7c}cos(cq) \)
\( E_q^3 = -50 + 17,885e^{-3.62c}cos(cq) \)
Does this look reasonable?
Very nice post! Let's discuss and critique these results here in these comments! I would like to see comments from pretty much everyone!
ReplyDeleteThis all looks great.
ReplyDeleteIs the fact that the band width goes to 0 as c goes to infinity something to do with when you have them infinitely far apart it is as if you are simply looking at one by itself? Therefore \(E_{q} = E_{0} \).
Also, I am still slightly uncertain what q represents. C