Compound 6,6′‐([1]benzothieno[3,2‐b][1]benzothiophene‐2,7‐diyl)bis(butan‐1‐ol) (BTBT‐C4OH) displays a continuous type 0 first‐order isosymmetric phase transition at 200 K which is accompanied by a continuous change of the thermal expansion along the b axis from positive to negative. The equivalent isotropic atomic displacement parameters for all non‐hydrogen atoms as well as all the eigenvalues of the anisotropic atomic displacement tensor show discontinuous behavior at the phase transition. The eigenvalues of the translational tensor in a rigid‐body description of the molecule are all discontinuous at the phase transition, but the librational eigenvalues are discontinuous only in their temperature derivative. BTBT‐C4OH displays a similar type of quasi‐supercritical phase transition as bis(hydroxyhexyl)[1]benzothieno[3,2‐b][1]benzothiophene (BTBT‐C6OH), despite the difference in molecular packing and the very large difference in thermal expansion magnitudes.

中文翻译：

---

有机苯并噻吩并苯并噻吩结构中的正负单轴热膨胀交叉。

化合物6,6'-（[[1] benzothieno [3,2- b ] [1] benzothiophene-2,7 -diyl）bis（butan -1-ol）（BTBT-C4OH）显示连续0型一阶在200 K时出现等对称相变，伴随着沿b轴的热膨胀从正到负连续变化。所有非氢原子的等效各向同性原子位移参数以及各向异性原子位移张量的所有特征值在相变处表现出不连续的行为。在分子的刚体描述中，平移张量的特征值在相变处都是不连续的，但是自由特征值仅在其温度导数上是不连续的。BTBT-C4OH尽管分子堆积不同且热膨胀差异很大，但仍显示出与双（羟基己基）[1]苯并噻吩并[3,2- b ] [1]苯并噻吩（BTBT-C6OH）类似的准超临界相变类型数量级。