Table 3. Parameters obtained by fitting of equations (1) and (2) to the unit-cell parameters and unit-cell volume of α-ammonium carbamate between 4.2 and 180 K.

	X 0 (Å, Å3)	P (×10−4)	q	r (×10−4)	s	Adjusted R 2
a axis	17.0517 (2)	–	–	0.268 (8)	−51 (2)	0.99827
b axis	6.43539 (9)	0.95 (1)	−14.5 (3)	–	–	0.99973
c axis	6.68077 (6)	–	–	0.74 (2)	−113 (3)	0.99903
Volume (Å3)	733.148 (9)	–	–	1.65 (1)	−60.9 (6)	0.99993