Two-component system CCl4 + (CH3)3CBr: extrema in equilibria involving orientationally disordered phases.
Two-component system CCl4 + (CH3)3CBr: extrema in equilibria involving orientationally disordered phases.
复制标题
双组分系统 CCl4 (CH3)3CBr：涉及定向无序相的平衡极值。
DOI：
10.1021/jp061484
复制
发表时间：
2006
影响因子：
3.3
通讯作者：
D. Mondieig
中科院分区：
文献类型：
--
作者：
M. Barrio;L. C. Pardo;J. Tamarit;P. Négrier;J. Salud;D. López;D. Mondieig
用X射线粉末衍射和热分析技术测定了四氯化碳（CCl_4）和2-甲基-2-溴甲烷（（CH_3）_3CBr）二元体系从210 K到液态的取向无序相和液相相平衡。（CH_3）_3CBr的OD稳定面心立方（FCC）相和CCl_4的亚稳面心立方（FCC）相之间的同构关系已通过晶格参数的连续演化和在整个组成范围内的两相平衡[FCC + L]的存在而得到证实，尽管CCl_4组分的FCC相相对于其OD菱面体（R）稳定相具有单向性。发现了一系列连续的OD-R混晶，证实了（CH_3）_3CBr的OD相Ⅱ具有R晶格对称性，而这一点长期以来一直被晶体学结果所误解。根据Rudman最近获得的单晶结果（Rudman，R. J. Mol. Struct.2001，569，157）。此外，还给出了一些实验证据，以证实每个晶胞（Z = 21）的分子数。热力学评估再现连贯的相图稳定的[R + L]和[R + FCC]两相平衡，以及部分亚稳[FCC + L]两相平衡，并提供了一组数据的热力学性质的非实验可用的纯组分的相变。令人惊讶的是，涉及R和FCC OD相的相平衡似乎是极少数显示具有两个极端的固-固平衡的相平衡之一。
Phase equilibria involving orientationally disordered (OD) and liquid phases of the two-component system between carbon tetrachloride (CCl4) and 2-methyl-2-bromomethane ((CH3)3CBr) have been determined by means of X-ray powder diffraction and thermal analysis techniques from 210 K up to the liquid state. The isomorphism relation between the OD stable face-centered cubic (FCC) phase of (CH3)3CBr and the metastable FCC phase of CCl4 has been demonstrated throughout the continuous evolution of the lattice parameters and the existence of the two-phase equilibrium [FCC + L] for the whole range of composition, despite the monotropy of the FCC phase for the CCl4 component with respect to its OD rhombohedral (R) stable phase. A continuous series of OD R mixed crystals is found, which confirms the R lattice symmetry of the OD phase II of (CH3)3CBr, for which the crystallographic results have been long-time misinterpreted. X-ray patterns of such a phase were indexed according to the recent single-crystal results obtained by Rudman (Rudman, R. J. Mol. Struct. 2001, 569, 157). In addition, some experimental evidences are given to confirm the number of molecules per unit cell (Z = 21). The thermodynamic assessment reproduces coherently the phase diagram for the stable [R + L] and [R + FCC] two-phase equilibria as well as for the partially metastable [FCC + L] two-phase equilibrium and provides a set of data for the thermodynamic properties of nonexperimentally available phase transitions of pure components. Surprisingly, the phase equilibrium involving R and FCC OD phases appears as one of the very few showing a solid-solid equilibrium with two extremes.