Understanding tight binding model

[mkbh_10]

Explain to me the Fig 10.6 given on page 184 in Ashcroft and Mermin.
How is line along gamma k not doubly degenerate and line along gamma L doubly degenerate ?

 

[Deadpeng]

Ashcroft is a bit long on text and short on pictures. What the diagram means is that it is actually showing the Energy values for a d orbital which should give 5 lines. Notice that in the first 2 diagrams there are only 3 and 4 each because of degeneracy. In other words, the solutions overlap