Hi. What I'm trying to do is to obtain the energy spectrum from the following dispersion relation:(adsbygoogle = window.adsbygoogle || []).push({});

[tex]E^4-A·E^3+B·E^2-C·E+D-F·E^2·cos(k·a_0)^2+G·E·cos(k·a_0)^2-H·cos(k·a_0)^2 = 0[/tex]

where E is the energy, k is the wave vector and a0 the distance between adjacent neighbors in a 1-Dimensional lattice with a two-atom basis, with some weird on-site energies.

Given the following model parameters:

A = -48.37528081

B = +877.6426691

C = -7077.321036

D = +21403.79575

F = -0.00002232761528

G = +0.0005479196789

H = -0.003361487230

I keep getting imaginary energies! What I do is simply solve the equation for E given some values for k. Am I doing it wrong? Or the parameters must be wrong? Please help! :(

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Energy spectrum from dispersion relation E(k)

**Physics Forums | Science Articles, Homework Help, Discussion**