Simple tight-binding treatment

It should be noted here that the overall shape of the K-phase FS can also be obtained by a simple free-electron treatment. With the usual parabolic bands and the known electron density one obtains a circular FS which cuts the Brillouin zone at approximately the point where the calculated gaps in Fig, 2.19 occur. Folding back these FS parts into the first Brillouin zone results in an only slightly modified topology compared to the calculated tight-binding FS of K-(ET)2l3. The effective masses estimated from the predicted band-structures are close to the free-electron mass, rrie. These values, however, are in contradiction to the experimentally extracted masses from optical [165, 166] and also dHvA or SdH measurements (see Sect. 4.2). 

Some time ago Schmidt and Korzeniewski [11] presented a simple onedimensional tight binding limit analysis of the problem of band states for ionic conduction. Although the potential energy function used was harmonic, delocalization was considered in the same manner as was used years ago in the Wall-Glockler [41] analysis of the inversion doubling of ammonia. Because of the simplicity of the calculation, and its ease of application, I summarize it here. The treatment is limited, at this... 

---