Electronic properties of alkali trimers

The electronic properties of the alkali trimers Li₃, Na ₃, and K₃ are studied using the pseudopotential and the local-spin-density approximations. More than 100 configurations were calculated for each trimer in order to obtain a complete picture of the adiabatic Born-Oppenheimer surfaces. The equilibrium geometry of the trimers are Jahn-Teller distortions of an equilateral triangle. Although the three surfaces are quite similar, Li₃ is more affected than Na₃ or K ₃ by the dynamical character of the Jahn-Teller distortion. The calculated ionization potentials agree very well with the experimental values and the qualitative features of the Born-Oppenheimer surface are confirmed by recent ESR experiments.