To examine the effects of chemical composition on thermal expansion in the pyroxene mineral group, X-ray diffraction data have been collected from room temperature to ~925 °C on a chemically diverse group of 13 pyroxenes including four orthorhombic and nine monoclinic samples. Additionally, resulting unit-cell volumes computed from the XRD data have proven to be good tests for a large number of thermal expansion models; the physical model by Kroll and coworkers and the empirical one by Fei have been found to be especially useful. Modeling also has allowed the connection of present data, collected at temperatures above 25 °C, to the volume data of other workers for much lower temperatures, well below 0 °C, and also extrapolation of values for volume and thermal expansion well beyond the measurement range.We have found for orthopyroxenes that Fe2+-Mg2+ substitution has little effect on thermal expansion coefficients for volume. For clinopyroxenes, however, greater thermal expansion occurs in Ca2+-(diopside, augite, hedenbergite, johannsenite) than in Li+-(spodumene) or Na+-bearing members (jadeite, aegirine, kosmochlor). Present data support the observation that differences in volume thermal expansion relate primarily to differences in expansion along the b crystallographic axis. This apparently is due to the greater concentration of M1 polyhedra along the b crystallographic axis, where expansion differences can be related to the shared O1-O1 polyhedral edge and inter-oxygen repulsion that is made easier by divalent, as opposed to trivalent, cation occupancy of the M1 crystallographic site.

中文翻译：

---

辉石系统中矿物的热膨胀和各种热膨胀模型的检验

为了检查化学成分对辉石矿物组中热膨胀的影响，已在 13 种辉石组成的化学多样化组中收集了从室温到约 925 °C 的 X 射线衍射数据，其中包括四个斜方晶和九个单斜晶样品。此外，根据 XRD 数据计算得出的晶胞体积已被证明是对大量热膨胀模型的良好测试；发现 Kroll 及其同事的物理模型和 Fei 的经验模型特别有用。建模还允许将在高于 25 °C 的温度下收集的现有数据与远低于 0 °C 的更低温度下其他工人的体积数据联系起来，并且还可以推断出远远超出测量范围的体积和热膨胀值范围。我们发现对于斜方辉石，Fe2+-Mg2+ 取代对体积的热膨胀系数影响很小。然而，对于单斜辉石，Ca2+-（透辉石、辉石、海登堡辉石、约翰闪石）的热膨胀比含 Li+-（锂辉石）或 Na+ 的成员（硬玉、绿辉石、kosmochlor）的热膨胀更大。目前的数据支持这样的观察，即体积热膨胀的差异主要与沿 b 晶轴的膨胀差异有关。这显然是由于沿 b 晶轴的 M1 多面体浓度更大，其中膨胀差异可能与共享的 O1-O1 多面体边缘和氧间排斥有关，二价而不是三价阳离子占据更容易M1 晶体学位点。