The temperature dependence of the crystal structures of the solid halogens, bromine and chlorine
The temperature dependence of the crystal structures of the solid halogens, bromine and chlorine
复制标题
DOI：
10.1080/00268978400102741
复制
发表时间：
1984-11
影响因子：
1.7
通讯作者：
B. M. Powell;K. Heal;B. Torrie
中科院分区：
文献类型：
--
作者：
B. M. Powell;K. Heal;B. Torrie
采用中子粉末剖面细化技术测定了固体Br2在5、80、170和250 K和固体Cl2在22、55、100和160 K时的晶体结构。结果证实了这两种卤素在所有温度下都具有空间群Cmca，结构是同构的。对于这两种卤素，晶格参数a和b随温度单调增加，但晶格参数c在最高温度下减小。采用各向同性和各向异性热参数对数据进行了分析。分子内键长及其相对于b轴的取向随温度变化不大。在5 K时，Br2的键长为2·301(2)A，而A = 6·5672(3),b = 4·4678(2),c = 8·6938(4)A。在22 K时，Cl2的键长为1·994(2)A，而A = 6·1453(2),b = 4·3954(1),c = 8·1537(2)A，其中引用的误差是由轮廓拟合程序产生的误差。
The neutron powder profile refinement technique has been used to determine the crystal structure of solid Br2 at 5, 80, 170 and 250 K and that of solid Cl2 at 22, 55, 100 and 160 K. The results confirm that the structures of the two halogens are isomorphous, with space group Cmca at all temperatures. For both halogens the lattice parameters a and b increase monotonically with temperature, but the lattice parameter c decreases at the highest temperatures. The data were analysed assuming both isotropic and anisotropic thermal parameters. The intramolecular bond length and its orientation relative to the b-axis show little change with temperature. For Br2 at 5 K the bond length is 2·301(2) A while a = 6·5672(3), b = 4·4678(2), c = 8·6938(4) A. For Cl2 at 22 K the bond length is 1·994(2) A while a = 6·1453(2), b = 4·3954(1), c = 8·1537(2) A, where the errors quoted are those produced by the profile fitting program.