NH4NO3 I ($G0_{8}$) Structure : AB_cP2_221_a_b

Picture of Structure; Click for Big Picture
Prototype : NH4NO3
AFLOW prototype label : AB_cP2_221_a_b
Strukturbericht designation : $G0_{8}$
Pearson symbol : cP2
Space group number : 221
Space group symbol : $Pm\bar{3}m$
AFLOW prototype command : aflow --proto=AB_cP2_221_a_b
--params=
$a$


  • Ammonium Nitrate exists in a variety of forms, (Hermann, 1937) depending on the temperature: \[\begin{array}{ccccc} \text{ Phase } & \text{ Temperature ${^\circ}$C } & \text{ Strukturbericht } & \text{ Page } \\ \text{ I } &\text{ 125 $--$ 170 } &\text{ $G0_{8}$ } &\href{\WEBSITEPREFIX/AB_cP2_221_a_b.NH4.NO3.html}{\text{AB_cP2_221_a_b.NH4.NO3}} &\text{ (this structure) } \\ \text{ II } &\text{ 84 $--$ 125 } &\text{ $G0_{9}$ } &\href{\WEBSITEPREFIX/ABC3_tP10_100_b_a_bc.html}{\text{ABC3_tP10_100_b_a_bc}} &\text{ } \\ \text{ III } &\text{ 32 $--$ 84 } &\text{ $G0_{10}$ } &\href{\WEBSITEPREFIX/ABC3_oP20_62_c_c_cd.N.NH4.O.html}{\text{ABC3_oP20_62_c_c_cd.N.NH4.O}} &\text{ } \\ \text{ IV } &\text{ -17 $--$ 32 } &\text{ $G0_{11}$ } &\href{\WEBSITEPREFIX/A4B2C3_oP18_59_ef_ab_af.html}{\text{A4B2C3_oP18_59_ef_ab_af}} &\text{ } \\ \text{ V } &\text{ $< -17$ } &\text{ Gwihabaite } &\href{\WEBSITEPREFIX/A4B2C3_tP72_77_8d_ab2c2d_6d.html}{\text{A4B2C3_tP72_77_8d_ab2c2d_6d2}} &\text{ }\end{array}\]
  • In the $G0_{8}$ structure, both the NH4+ and NO3 ions rotate freely about their centers of mass (Kracek, 1931). The two ions sit on the same sites as atoms in the CsCl ($B2$) structure.

Simple Cubic primitive vectors:

\[ \begin{array}{ccc} \mathbf{a}_1 & = & a \, \mathbf{\hat{x}} \\ \mathbf{a}_2 & = & a \, \mathbf{\hat{y}} \\ \mathbf{a}_3 & = & a \, \mathbf{\hat{z}} \\ \end{array} \]

Basis vectors:

\[ \begin{array}{ccccccc} & & \mbox{Lattice Coordinates} & & \mbox{Cartesian Coordinates} &\mbox{Wyckoff Position} & \mbox{Atom Type} \\ \mathbf{B}_{1} & = & 0 \, \mathbf{a}_{1} + 0 \, \mathbf{a}_{2} + 0 \, \mathbf{a}_{3} & = & 0 \, \mathbf{\hat{x}} + 0 \, \mathbf{\hat{y}} + 0 \, \mathbf{\hat{z}} & \left(1a\right) & \mbox{NH$_{4}$} \\ \mathbf{B}_{2} & = & \frac{1}{2} \, \mathbf{a}_{1} + \frac{1}{2} \, \mathbf{a}_{2} + \frac{1}{2} \, \mathbf{a}_{3} & = & \frac{1}{2}a \, \mathbf{\hat{x}} + \frac{1}{2}a \, \mathbf{\hat{y}} + \frac{1}{2}a \, \mathbf{\hat{z}} & \left(1b\right) & \mbox{NO$_{3}$} \\ \end{array} \]

References

  • F. C. Kracek, S. B. Hendricks, and E. Posnjak, Group Rotation in Solid Ammonium and Calcium Nitrates, Nature 128, 410–411 (1931), doi:10.1038/128410b0.

Found in

  • C. Hermann, O. Lohrmann, and H. Philipp, eds., Strukturbericht Band II 1928–1932 (Akademische Verlagsgesellschaft M. B. H., Leipzig, 1937).

Geometry files


Prototype Generator

aflow --proto=AB_cP2_221_a_b --params=

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