通常使用单独的样品收集单晶X射线和中子衍射数据。当在高压下研究样品时,这是一个缺点,因为在两个单独的实验中很难达到完全相同的压力,特别是如果中子数据是使用劳厄方法收集的,其中无法测量晶胞尺寸的精确绝对值来检查压力的接近程度。在这项研究中,衍射数据已收集在相同的条件下对硫酸铜(II)五水合物的相同样品,使用常规的实验室衍射仪和X射线源进行X射线测量,并在ANSTO设施中使用Koala单晶Laue衍射仪进行中子测量。样本,尺寸为0.40×0.22×0.20mm3,并保持在0.71GPa的压力下,包含在一个微型的美林-巴西特钻石砧座细胞中。通过微型电池的金属体以及钻石的高穿透性衍射中子束产生了适合结构细化的数据,并补偿了X射线测量的低完整性,由于样品的三斜对称和细胞对倒数空间的遮蔽,这一比例仅为24%。这两个数据集组合在一个单一的“XN”结构细化中,其中所有原子,包括H原子,用各向异性位移参数进行了细化。与分别使用X射线或中子数据进行细化相比,在XN细化中,结构参数的精度提高了50%。
Single-crystal X-ray and neutron diffraction data are usually collected using separate samples. This is a disadvantage when the sample is studied at high pressure because it is very difficult to achieve exactly the same pressure in two separate experiments, especially if the neutron data are collected using Laue methods where precise absolute values of the unit-cell dimensions cannot be measured to check how close the pressures are. In this
study, diffraction data have been collected under the same conditions on the same sample of copper(II) sulfate pentahydrate, using a conventional laboratory diffractometer and source for the X-ray measurements and the Koala single-crystal Laue diffractometer at the ANSTO facility for the neutron measurements. The sample, of dimensions 0.40 × 0.22 × 0.20 mm3 and held at a pressure of 0.71 GPa, was contained in a miniature Merrill-Bassett diamond-anvil cell. The highly penetrating diffracted neutron beams passing through the metal body of the miniature cell as well as through the diamonds yielded data suitable for structure refinement, and compensated for the low completeness of the X-ray measurements, which was only 24% on account of the triclinic symmetry of the sample and the shading of reciprocal space by the cell. The two data-sets were combined in a single \'XN\' structure refinement in which all atoms, including H atoms, were refined with anisotropic displacement parameters. The precision of the structural parameters was improved by a factor of up to 50% in the XN refinement compared with refinements using the X-ray or neutron data separately.