Insights from experiment and ab initio calculations into the glasslike transition in the molecular conductor kappa-(BEDT-TTF)(2)Hg(SCN)(2)Cl

Article

关键词: ORGANIC SUPERCONDUCTORS;    THERMAL-EXPANSION;    INSULATOR-TRANSITION;    SYSTEM;    CRYSTALS;    BEHAVIOR;    NMR;   

DOI  :  10.1103/PhysRevB.97.075115

来源: SCIE

【 摘 要 】

We present high-resolution measurements of the relative length change as a function of temperature of the organic charge-transfer salt kappa-(BEDT-TTF)(2)Hg(SCN)(2)Cl. We identify anomalous features at T-g approximate to 63 K which can be assigned to a kinetic glasslike ordering transition. By determining the activation energy E-A, this glasslike transition can be related to conformational degrees of freedom of the ethylene endgroups of the organic building block BEDT-TTF. As opposed to other kappa-(BEDT-TTF)(2)X salts, we identify a peculiar ethylene endgroup ordering in the present material in which only one of the two crystallographically inequivalent ethylene endgroups is subject to glasslike ordering. This experimental finding is fully consistent with our predictions from ab initio calculations from which we estimate the energy differences Delta E and the activation energies E-A between different conformations. The present results indicate that the specific interaction between the ethylene endgroups and the nearby anion layers leads to different energetics of the inequivalent ethylene endgroups, as evidenced by different ratios E-A/Delta E. We infer that the ratio E-A/Delta E is a suitable parameter to identify the tendency of ethylene endgroups toward glasslike freezing.

【 授权许可】

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