Walsh Aron, Watson Graeme W
Department of Chemistry, University of Dublin, Trinity College, Dublin 2, Ireland.
J Phys Chem B. 2005 Oct 13;109(40):18868-75. doi: 10.1021/jp051822r.
The electronic structure of SnO, SnS, SnSe, and SnTe in the rocksalt, litharge, and herzenbergite structures has been calculated using density functional theory. Comparison of the distorted and undistorted structures allows for an explanation of the unusual experimentally observed structural transitions seen along the Sn(II) monochalcogenides. Analysis of the electronic structure shows a strong anion dependence of the Sn(II) lone pair, with the Sn(5s) and Sn(5p) states too far apart to couple directly. However, the interaction of Sn(5s) with anion states of appropriate energy produce a filled antibonding Sn(5s)-anion p combination which allows coupling of Sn(5s) and Sn(5p) to occur, resulting in a sterically active asymmetric density on Sn. While the interaction between Sn(5s) and O(2p) is strong, interactions of Sn with S, Se, and Te become gradually weaker, resulting in less high energy 5s states and hence weaker lone pairs. The stability of the distorted structures relative to the symmetric structures of higher coordination is thereby reduced, which induces the change from highly distorted litharge SnO to highly symmetric rocksalt SnTe seen along the series.
利用密度泛函理论计算了岩盐结构、密陀僧结构和黑硫锡矿结构中的SnO、SnS、SnSe和SnTe的电子结构。对畸变结构和未畸变结构的比较有助于解释沿Sn（II）单硫属化物观察到的异常实验结构转变。电子结构分析表明，Sn（II）孤对电子对阴离子有强烈的依赖性，Sn（5s）和Sn（5p）态相距太远，无法直接耦合。然而，Sn（5s）与具有适当能量的阴离子态的相互作用产生了一个充满的反键Sn（5s）-阴离子p组合，这使得Sn（5s）和Sn（5p）能够发生耦合，从而在Sn上产生一个空间活性不对称密度。虽然Sn（5s）与O（2p）之间的相互作用很强，但Sn与S、Se和Te之间的相互作用逐渐减弱，导致高能5s态减少，因此孤对电子对也减弱。相对于高配位对称结构，畸变结构的稳定性因此降低，这导致了沿该系列观察到的从高度畸变的密陀僧SnO到高度对称的岩盐SnTe的变化。
