The currently most sensible definition of an atomic volume in a chemical system is given by the volume of the electron density basin around the atomic electron density maximum. This corresponds to the QTAIM (R.F.W. Bader) definition of an atom in a molecule.
The QTAIM basins cover just one aspect of the 
ChemBond in Physical Space research. Electron delocalization and electron localizability represent two further electronic quantities for characterization.
The volume chemistry project has strong overlap with crystal chemistry, and it serves to further extend the original ideas of Wilhelm Biltz. In a cooperation with Prof. Dr. W. Bronger a few results have been published along this line.
Publications:
- W. Bronger, R. Kniep, M. Kohout, "Volume Chemistry of Nitrogen in Binary metal Nitrides and Subnitrides", Z. Anorg. Allg. Chem. 2004, 630, 117-121.
- W. Bronger, R. Kniep, M. Kohout, "Zur Raumchemie des Wasserstoffs in binären und ternären Metallhydriden", Z. Anorg. Allg. Chem. 2005, 631, 265-271.
- W. Bronger, A. Baranov, F.R. Wagner, R. Kniep, "Atomic Volumina and Charge Distribution in Nitridometalates", Z. Anorg. Allg. Chem. 2007, 633, 2553-2557.
- A. Baranov, M. Kohout, F.R. Wagner, Yu. Grin, W. Bronger, "Spatial Chemistry of the Aluminium--Platinum Compounds: a Quantum Chemical Approach", Z. Kristallogr. 2007, 222, 527-531.
- A. Baranov, M. Kohout, F.R. Wagner, Yu. Grin, R. Kniep, W. Bronger, "On the Volume Chemistry of Solid Compounds: the Legacy of Wilhelm Biltz", Z. Anorg. Allg. Chem. 2008, 634, 2747-2753.