W0421

α-NTO – A 4-component Triclinic Twin. Nadezhda B. Bolotina, Kristin Kirschbaum and A. Alan Pinkerton, Dept. of Chemistry, Univ. of Toledo, Toledo, OH 43606.

NTO (5-nitro-2,4-dihydro-3H-1,2,4,-triazol-3-one) is an explosive compound with low impact sensitivity. Two solid phases of NTO are known, α and β. Although α-NTO is the stable dominating form, its crystal structure determination has proven difficult, whereas the metastable β form has been well studied. We have determined that the difficulty in structure solution of the alpha form is due to twinning. The structure may be described in a primitive triclinic unit cell with parameters a = 5.1233(8), b = 10.314(2) Å, c = 17.998(3), α = 106.609(2), β = 97.813(2), γ = 90.131(2)°, space group P. The lattice transformation a' = a, b' = b, c' = a + b + 2c gives an I-centered pseudo-orthorhombic unit cell. Four triclinic components can be obtained by applying the twin laws associated with the two-fold rotations of the orthorhombic pseudo-cell. Integrating the close-to-overlapped reflections with a large box allowed the structure to be solved and refined as a four-fold twin to wR = 0.0435 for 3571 reflections with intensities I > 3σ(I). Currently we are attempting to index and integrate the four components separately.