Reference : Phase transition between cubic and monoclinic polymorphs of the tetracyanoethylene cr...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Chemistry
http://hdl.handle.net/10993/25179
Phase transition between cubic and monoclinic polymorphs of the tetracyanoethylene crystal: the role of temperature and kinetics
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Schatschneider, Bohdan [Department of Chemistry, The Pennsylvania State University, Fayette- The Eberly Campus, 1 University Dr, Uniontown, PA, 15401, USA]
Liang, Jian-Jie [Accelrys, Inc., 10188 Telesis Court, Suite 100, San Diego, CA, 92121, USA]
Jezowski, Sebastian [Department of Chemistry, The University of California, Riverside, CA, 92501, USA]
Tkatchenko, Alexandre mailto [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6,14195, Berlin, Germany > > > ; Department of Chemistry, Pohang University of Science and Technology, Pohang 790–784, Korea]
2012
CRYSTENGCOMM
ROYAL SOC CHEMISTRY
14
14
4656-4663
Yes (verified by ORBilu)
International
1466-8033
THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS ENGLAND
[en] 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 N vibrons.
http://hdl.handle.net/10993/25179
10.1039/c2ce25321f
Article

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