Inversion of AX3 and AX4 pyramidal and tetrahedral molecules

A review is presented of precision ab initio calculations, carried out mostly for the recent 5-8 years, of inversion rearrangements in pyramidal and tetrahedral AX3 and AX4 molecules having two equivalent configurations, produced from each other by inversion. It is noted that precision nonempirical calculations enabled to compile large and reliable data on inversion barriers (hsub(inv.)) of molecules being studied, including B1-Be compounds, halogenides of transition metals. On the basis of these data general trends in hsub(inv.) changes are traced and instances of inversion molecular flexibility are noticed