The crystal structure of α-manganese
The crystal structure of α-manganese
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DOI：
10.1098/rspa.1927.0103
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发表时间：
1927-07-01
期刊：
影响因子：
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通讯作者：
Thewlis, J
中科院分区：
文献类型：
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作者：
Bradley, AJ;Thewlis, J
Westgren和phragmsamen以及现在的一位作者已经独立地证明了锰是同素异形体的。两项研究都指出存在三种晶体修饰。在这两篇论文中，对不同形式的金属的命名并不相同，为了避免歧义，我们采用了Westgren和phragmsamen的命名法。后者更可取，因为所谓的电解锰，我们称之为α-锰（它们的γ-锰）可能是金属的氢化物。因此，把α-锰和β-锰这两种已知的金属形式命名为α-锰和β-锰似乎更好，正如w和p所做的那样。本文描述了α-锰的结构，它在室温和高达700℃的高温下都是稳定的。在上述两项调查中，仅采用了x射线分析的粉末法。为了使任何分析方法的结果可信，该方法必须能够区分所有理论上可能的解，而仅仅指出一个解释观察结果的解是不够的。如果实验数据不广泛，而且测试的精度很低，很容易在观测和计算之间得到虚假的一致，这完全在实验误差的范围内。这对于α-锰这样的结构来说尤其如此，因为它的晶胞含有大量的原子，而原子的位置取决于大量的参数。
It has been shown independently by Westgren and Phragmén, and by one of the present authors, that manganese is allotropic. Both investigations pointed to the existence of three crystalline modifications. The names given to the different forms of the metal were not the same in the two papers, and in order to avoid ambiguity we have adopted Westgren and Phragmén’s nomenclature. This latter is preferable because the so-called electrolytic manganese, which we called α-manganese (their γ-manganese) is probably a hydride of the metal. It therefore seems better to give the names α-manganese and β-manganese to the two forms which are known to be metallic, as W. and P. have done. The present paper describes the structure of α-manganese, which is stable at room temperature and higher temperatures up to about 700°C. In the two investigations referred to above, the powder method of X-ray analysis alone was employed. In order that the results of any method of analysis may be trustworthy, the method must be capable of discriminating between all solutions which are theoretically possible, and it is not sufficient merely to indicate one solution which explains the observations. If the experimental data are not extensive, and the accuracy with which they can be tested is low, it is easy to get a spurious agreement between observation and calculation, which lies well within the limits of experimental error. This is especially the case with a structure such as that of α-manganese where the unit cell contains a large number of atoms, and the atomic positions depend upon a large number of parameters.