Band structure of clusters

[abhishek_sharmacct]

Dear all
       Please tell me that how to calculate fermi energy and band structure of small nano clusters in place of bulk configuration(which provide bulk band structure and band gap) using 2008.10 version.
Also provide some theoretical material to learn detailed analysis of cluster properties using band structure.
Your help is very valuable for me.

Thanks

[zh]

In principle, the band structure is meaningful only for a system with periodicity. For a nanocluster system, it is zero-dimensional system and thus no band structure for such system. One can do the calculation of eigenvalues of a nanocluster system, as a molecule system.

[abhishek_sharmacct]

But it is a fact that as size decreases the band gap increases. And band gap is significantly increased at nano level as compared to bulk.
Band gap have meaning only when there some band exists. Hence there must be some band structure or energy levels for nanoclusters.

I have tried to calculate it as molecular system but when i try to drag crystal structure from bulk builder to molecular builder than nothing happens.
Please solve my problem.

[abhishek_sharmacct]

Please tell me also that which formula is used by ATK to obtain the band structure.

[Nordland]

The bandstructure is a result of the eigenvalues to the generalized eigenvalue problem H - eS = 0.

Which version are you using =?

[zh]

But it is a fact that as size decreases the band gap increases. And band gap is significantly increased at nano level as compared to bulk.
Band gap have meaning only when there some band exists. Hence there must be some band structure or energy levels for nanoclusters.

I have tried to calculate it as molecular system but when i try to drag crystal structure from bulk builder to molecular builder than nothing happens.
Please solve my problem.

Only the energy levels are available for the nanocluster. The band structure can be thought as the k-dependent energy levels for a crystal. For the simulation of a  nanocluster, only a Gamma point is enough if a supercell (e.g., a periodic configuration with large vacuum region, and the nanocluster is put in the center of this kind of configuration). The energy gap is the energy difference between the lowest unoccupied energy level and the highest occupied energy level.   Alternatively, the nanocluster can also be simulated as a molecule configuration.

Please refer to this webpage: "http://en.wikipedia.org/wiki/Electronic_band_structure", to clarify the understanding of the definition of band structure.

The crystal structure from bulk builder cannot be exported to the molecular builder. One can prepare a xyz file from the script file generated by bulk builder, and then load this xyz file by the molecular builder.