Flucytosine, CAS #2022-85-7, crystallizes in the tetragonal space group P41212 (#94) with a = 6.643768(27), c = 23.89009(10) Å, V = 1054.500(7) Å3, and Z = 8. In this work, the sample was obtained from the United States Pharmacopeial Convention (USP) Lot #R03100 and analyzed as-received. The room temperature (295 K) crystal structure was refined using synchrotron (λ = 0.412826 Å) powder diffraction data and optimized using the density functional theory (DFT). When looking down the a-axis, the crystal structure consists of multiple ribbon-like structures stacked into columns. The powder X-ray diffraction pattern of the compound has been submitted to ICDD® for inclusion in the Powder Diffraction File™ (PDF®). The agreement of the Rietveld-refined and DFT-optimized structures is good, with the largest difference in the external amine group with an overall root mean displacement of 0.056 Å. There is also evidence of unit cell expansion at higher temperatures, as the volume of the unit cell at 298 K was 1.6–1.9% greater than the two unit cells obtained at 150 K. A N–H⋯O hydrogen bond exists in the inter-ribbon region between the flucytosine molecules, resulting in a 3D hydrogen bond network.

中文翻译：

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氟胞嘧啶的粉末 X 射线衍射，C4H4FN3O

氟胞嘧啶，CAS #2022-85-7，在四方空间群中结晶磷41212 (#94) 与一种= 6.643768(27),C= 23.89009(10) 埃，五= 1054.500(7) Å3， 和Z= 8. 在这项工作中，样品取自美国药典 (USP) 批号 #R03100，并按原样进行分析。室温（295 K）晶体结构使用同步加速器（λ= 0.412826 Å) 粉末衍射数据并使用密度泛函理论 (DFT) 进行优化。往下看的时候一种轴，晶体结构由堆叠成柱状的多个带状结构组成。该化合物的粉末 X 射线衍射图已提交给 ICDD® 以包含在粉末衍射文件™ (PDF®) 中。Rietveld 精制和 DFT 优化结构的一致性很好，外部胺基的差异最大，总均根位移为 0.056 Å。也有在较高温度下晶胞膨胀的证据，因为在 298 K 时晶胞的体积比在 150 K 时获得的两个晶胞的体积大 1.6-1.9%。AN-H⋯O 氢键存在于氟胞嘧啶分子之间的带状区域，形成 3D 氢键网络。