Density functional theory calculations have been performed on SnO in the litharge, herzenbergite, and rocksalt crystal structures. An asymmetric electron distribution was found around the Sn atoms in litharge and herzenbergite SnO which could be ascribed to a Sn 5s2 sterically active "lone pair." Analysis of the electronic structure shows that the states responsible for the asymmetric Sn electron distribution are due to the coupling of unfilled Sn(5p) with the antibonding combination arising from interaction of Sn(5s) and O(2p). The coupling of Sn(5p) was found to be active in both the formation of the asymmetric density and the stabilization of the litharge and herzenbergite phases. Due to the symmetry of the interaction the coupling of Sn(5p) with the antibonding states can only take place on distorted Sn sites, explaining the absence of an asymmetry in the rocksalt structure. In contrast to the classical view that the Sn(II) "lone pair" forms directly through hybridization of Sn 5s and 5p, our calculations confirm for the first time, through COOP analysis, that it is only through the interaction of the oxygen 2p states that formation of the asymmetric density is achieved.
|Number of pages
|Physical Review B - Condensed Matter and Materials Physics
|Published - Dec 2004
Bibliographical noteFunding Information:
The authors would like to acknowledge the HEA for a PRTLI (Cycle III) grant, TCD for a Trinity College Postgraduate Studentship and Compaq and JREI (JR99BAPAEQ) for funding to purchase and support a 20 processor Compaq SC cluster at the Rutherford Appleton Laboratory. The authors would also like to thank Dr. Peter Oliver at RAL for access and assistance with Hrothgar, a 16 node Beowulf cluster.