Phase transition between cubic and monoclinic polymorphs of the tetracyanoethylene crystal: the role of temperature and kinetics
Phase transition between cubic and monoclinic polymorphs of the tetracyanoethylene crystal: the role of temperature and kinetics
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四氰乙烯晶体的立方晶型和单斜晶型之间的相变：温度和动力学的作用
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
A. Tkatchenko
中科院分区：
文献类型：
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作者：
Bohdan Schatschneider;Jian;S. Jezowski;A. Tkatchenko
分子结晶多晶型物的相对稳定性和相变行为的预测受到高度关注，因为不同的相可以拥有不同的物理和化学性质，同时具有相似的能量。众所周知，结晶四氰乙烯（TCNE，C6N4）在不同的热力学条件下表现出丰富的固态相行为，对此系统进行的大量实验研究证明了这一点。尽管如此，温度和动力学对 TCNE 相图的作用仍然知之甚少。在这里，第一性原理计算和高分辨率傅里叶变换红外 (HR-FTIR) 光谱实验用于研究 TCNE 立方相和单斜相随温度变化的相对稳定性。具体而言，采用密度泛函理论以及Tkatchenko和Scheffler的范德华相互作用方法(DFT+vdW)。计算结构与实验结构之间的良好一致性证明了该方法的准确性。我们发现，立方相在 0 K 时是最稳定的多晶型，但在 160 K 时变得不如单斜相。这种温度引起的相变是根据紧密接触和振动熵随温度变化的变化来解释的。这些发现得到了 CN 振动子的温度依赖性 HR-FTIR 线宽研究的支持。
Prediction of the relative stabilities and phase transition behavior of molecular crystalline polymorphs is highly coveted as distinct phases can possess different physical and chemical properties while having similar energies. Crystalline tetracyanoethylene (TCNE, C6N4) is known to exhibit rich solid state phase behavior under different thermodynamic conditions, as demonstrated by a wealth of experimental studies on this system. Despite this fact, the role of temperature and kinetics on the phase diagram of TCNE remains poorly understood. Here, first-principles calculations and high-resolution Fourier-transformed infrared (HR-FTIR) spectroscopy experiments are used to study the relative stabilities of the cubic and monoclinic phases of TCNE as a function of temperature. Specifically, density-functional theory with the van der Waals interactions method of Tkatchenko and Scheffler (DFT+vdW) is employed. The accuracy of this approach is demonstrated by the excellent agreement between the calculated and experimental structures. We find that the cubic phase is the most stable polymorph at 0 K, but becomes less favorable than the monoclinic phase at 160 K. This temperature-induced phase transition is explained on the basis of varying close contacts and vibrational entropies as a function of temperature. These findings are supported by a temperature-dependent HR-FTIR linewidth study of the CN vibrons.
用于生物反应 d 轨道半经验计算的平滑溶剂化方法。
DOI：
10.1021/jp044061l
发表时间：
2005
期刊：
The journal of physical chemistry. B
影响因子：
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作者：
Gregersen,BrentA;Khandogin,Jana;Thiel,Walter;York,DarrinM
通讯作者：
York,DarrinM