  We report a new metastable gamma polymorph of mixed metal borohydride
LiSc(BH4)4. Using Density Functional Theory calculations with dispersion
corrections, we prove importance of van der Waals H...H interactions for
correct theoretical description of the title compound. We propose the ordered
ground state structure (alpha form) and revise the recently reported beta
phase, now describing it as a solid solution, LiSc(BH4)4-xClx, x~0.7. The
LiSc(BH4)4 polymorphism is rationalized using Zr(BH4)4 type structure with Sc
--> Zr and Li in the interstitial face-centered positions.
