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Hi

I am calculating the contribution of various atoms to particular energy bands. I employ p4v but since the data comes from VASP I figured the question applies here too.

When the band structure is projected onto particular atoms, the result is those yellow circles, the size of which is proportional to the weight of the contribution from those atoms to that state.

It is also possible to open up a spreadsheet in xmgrace and look at the actual numbers that produce the size of the circles.

There are two things I don't understand:

1. I projected onto two sets that together make up all the atoms but the weights did not add up to one. Indeed they sometimes didn't even make it to 1/2. Why is this? What do the numbers actually represent? (Are they simply in the correct ratio regardless of their size?)

2. For one structure I simulated, selecting all the atoms still produced the yellow circles which varied in size from large to negligible across the band structure. How can this be given that no atoms were left out? Again this raises the question as to what the numbers actually mean.

many thanks

Ben

These numbers correspond to the local charges as integrated from the charge densities in spheres centerd at the respective atoms' sites, with r=RWIGS. They are not rescaled. Therefore, as the volumns of these spheres do not add up to the volume of the unit cell, the weights do not add up to 1 either. All charge contributions of the interstitial (and, possibly, vacuum) region are not accounted for.