Table 1.

Observed and calculated lattice constants of ammonia phases I and IV.

Parameter	Expt. Phase I8 at 0 GPa, 2 K	MP2 Phase I at 0.1 GPa, 0 K	Expt. Phase IV6 at 5 GPa, 150 K	MP2 Phase IV at 5 GPa, 0 K
a/Å	5.048	4.923	3.250	3.142
b/Å	5.048	4.923	5.658	5.599
c/Å	5.048	4.923	5.356	5.445