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## Voronoi charge

Voronoi charge of each atom is calculated by integrating electron and spin densities in a Voronoi polyhedron. The Voronoi polyhedron is constructed from smeared surfaces which are defined by a Fuzzy cell partitioning method [49]. It should be noted that this Voronoi analysis gives often overestimated or underestimated charge, since Voronoi polyhedron is determined by only the structure without taking account of atomic radius. If you want to calculate Voronoi charge, specify the following keyword 'Voronoi.charge' in your input file:
```     Voronoi.charge      on       # on|off, default = off
```

In case of a methane molecule, the following Voronoi charges are output to '*.out'.

```***********************************************************
***********************************************************
Voronoi charges
***********************************************************
***********************************************************

Sum of Voronoi charges for up    =  3.999999031463
Sum of Voronoi charges for down  =  3.999999031463
Sum of Voronoi charges for total =  7.999998062926

Total spin S by Voronoi charges  =  0.000000000000

Up spin      Down spin     Sum           Diff
Atom=   1   1.137912511  1.137912511   2.275825021   0.000000000
Atom=   2   0.715521700  0.715521700   1.431043399   0.000000000
Atom=   3   0.715521486  0.715521486   1.431042973   0.000000000
Atom=   4   0.715521776  0.715521776   1.431043552   0.000000000
Atom=   5   0.715521559  0.715521559   1.431043118   0.000000000
```
Clearly, we see that carbon atom (Atom=1) and hydrogen atoms (Atom=2-5) tend to possess less charge and much charge, respectively, from a chemical sense. However, the Voronoi analysis could be a useful and complementary information for a bulk system with a closed pack structure.

t-ozaki 2013-05-22