ROLE OF THE MADELUNG ENERGY IN THE NEUTRAL IONIC PHASE-TRANSITION OF TETRATHIAFULVALENE CHLORANIL
ROLE OF THE MADELUNG ENERGY IN THE NEUTRAL IONIC PHASE-TRANSITION OF TETRATHIAFULVALENE CHLORANIL
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DOI：
10.1021/ja00287a021
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发表时间：
1985-01-01
影响因子：
15
通讯作者：
TORRANCE, JB
中科院分区：
文献类型：
--
作者：
METZGER, RM;TORRANCE, JB
为了阐明在电荷转移固体中是什么决定了电荷从供体到受体的转移程度，我们计算了四硫富瓦烯（TTF）四氯对苯醌晶体的静电马德隆能ε M，它是压力和温度的函数。在300 K下，在1 bar和11 kbar之间，其中存在中性和离子基态之间的跃迁，E M变得更负约0.10 eV。这种结合能的增加表明，压力依赖的马德隆能可能足够大，以驱动在高压下的中性-离子相变。在11 kbar下的电子量级为-3.8eV，表明中性态和离子态的计算能量在此压力下近似相等。另一方面，在300和50 K之间的1巴下，其中已经发现中性和离子基态之间的另一个跃迁，ε M变得更负仅约0.05 eV，或者是高压下跃迁的一半。这表明在低温下存在中性-离子转变的额外驱动力（我们认为这是堆栈的二聚化）。更好的定量协议的过渡和电荷转移带的能量得到正式包括在基态的部分电荷转移。
In order to elucidate what determines the degree of charge transfer from donorto acceptor in charge-transfer solids, we have calculated the crystalline electrostatic Madelung energy,£ M, for tetrathiafulvalene (TTF) chloranil as a function of pressure and temperature. At 300 K between 1 bar and 11 kbar, where there is a transition between Neutral and Ionic ground states,£ M becomes more negative by~ 0.10 eV. This increase in binding energy suggests that the pressure dependence of the Madelung energy may be sufficiently largeto drive the Neutral-Ionic phase transition at high pressures. Themagnitude of£ m=-3.8 eV at 11 kbar is used to show that the calculated energies of the Neutral and Ionic states become approximately equal at this pressure. On the other hand, at 1 bar between 300 and 50 K, where another transition between Neutral and Ionic ground states has been found,£ M becomes more negative by only~ 0.05 eV, or half as much as for the transition at high pressure. This suggests that there is an additional driving force for the Neutral-Ionic transition at low temperature (which we believe is the dimerization of the stacks). Better quantitative agreement for the transition and for the charge-transferband energy is obtained by formally including partial charge transfer in the ground state.