Ionic structures and the electric moment of LiH

There are two rather different questions that arise when considering ionic structures in VB wave functions. The first of these we discuss is the contribution to electric dipole moments. LiH is considered as an example. In the next section we take up ionic structures and curve crossings, using LiF to illustrate the points. 

LiH is the simplest uncharged molecule that has a permanent electric dipole moment. We examine here some of the properties of the simplest VB functions for this molecule. The molecule is oriented along the z-axis with the Li atom in the positive direction. 

The small moments in isotopic hydrogen, HD and HT, for example, do not interest us here. 

Covalent The dipole moment of the covalent stracture is never larger than 1 (in atomic units) and is always positive. A simple analysis is not so easy here, but the same Tils and His interaction as appeared above occurs in this case also. 

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