The structure of phase III ammonium nitrate

The vaporization of NH4NO3

“…Shinnaka [7] and Lucas et al [8] reported the AN II phase was stable between (84 and 125)°C with the tetragonal structure with space group P 42 1 m (a = 0.57193 nm and c = 0.49326 nm). The orthorhombic structure (Pnma) of the AN III phase with a = 0.77184 nm, b = 0.58447 nm and c = 0.0.71624 nm, was reported to be stable between (32 and 84)°C [9,10]. The low-temperature AN IV and AN V phases were reported as orthorhombic structure with space group Pmmn [stable (À16 to 32)°C] [8,11] and orthorhombic structure with space group Pccn (stable below À16°C) [12,13], respectively.…”

X-ray diffractometry studies and lattice parameter calculation on KNO3–NH4NO3 solid solutions

“…Pure KN has two different solid phases (KN II and KN I phases), and undergoes one solid-state phase transition. The detail experimental crystal structure information of AN and KN are given in Brown and McLaren (1962); Lucas et al (1979); Lucas et al (1980); Ahtee et al (1983); Nimmo and Lucas (1976); Nimmo and Lucas (1973). The crystal structure of AN III phase of pure NH 4 NO 3 was determined as orthorhombic structure and stable between 305.3 and 357 K—Goodwin et al (1947) determined the lattice parameters of this orthorhombic structure by X-ray diffraction method.…”

“…The crystal structure of AN III phase of pure NH 4 NO 3 was determined as orthorhombic structure and stable between 305.3 and 357 K—Goodwin et al (1947) determined the lattice parameters of this orthorhombic structure by X-ray diffraction method. Lucas et al (1980) reported the crystal structure of AN III phase as orthorhombic, space group P n m a , and a =0.77184(1) nm, b =0.58447(1) nm, and c =0.71624(1) nm ( Z =4) by the neutron diffraction study. Solid solution of the 5%KNO 3 in NH 4 NO 3 has also been determined as AN III phase at room temperature, and the detail structure studies are performed by X-ray diffraction (Holden et al , 1975) as well as neutron diffraction (Choi and Prask, 1980, 1982) methods.…”

Ab initio molecular dynamic study of solid-state transitions of ammonium nitrate

“…At normal pressure, AN exists in six phases at temperature range of 0–442 K. The lowest temperature phase VII is discovered in 1954 (below 103 K), which is further confirmed by Theoret and Sandorfy (below 213 K) 8 . Except phase VII, the crystallographic information of other five phases are determined using neutron diffraction: Pccn for phase V 9 10 (below 255 K); Pmmn for phase IV 11 12 13 (255–305 K); Pnma for phase III 13 14 (305–357 K); P 4/2 1 m for phase II 12 15 (357–398 K); and Pm3m for phase I 14 (398–442 K). The above five phases of AN are also differed by motional freedom and disorder of ammonium cations and nitrate anions 16 .…”

“…Both the crystal structure of AN and the behavior of [NH 4 ] + are significantly affected by temperature. In addition, phase IV-III transition only occurs in the presence of extremely little water; otherwise phase IV directly transforms into phase II 14 .…”