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首页> 外文期刊>Chemistry: A European journal >Vibronic Coupling in Molecules and in Solids
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Vibronic Coupling in Molecules and in Solids

机译：分子和固体中的振动耦合

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We uitilize the experience gained in our previous studies on the "chemistry of vibronic coupling" in simple homonuclear and heteronuclear molecules to begin assembling theoretical guidelines for the construction of potentially superconducting solids exhibiting large electron-phonon coupling. For this purpose we analyze similarities between vibronic coupling in isolated molecules and in extended solids. In particular, we study vibronic coupling along, the antisymmetric stretch coordinate (Q_as) in linear symmetric AAA molecules, and along the optical phonon "pairing" mode coordinate (Q_opt) in corresponding one-dimensional [A]_infinity chains built of equidistant A atoms. This is done for a broad range of chemical elements (A). The following similarities between vibronic coupling in molecules and phonon coupling in solids emerge from our calculations: 1) The HOMO/LUMO electronic energy gap in an AAA molecule incrases along Q_as, and the highest occupied crystal orbital/lowest unoccupied crystal orbital gap in [A]_infinity chain increases along Q_opt. 2) The maximum vibronic instability is invariably obtained for a half-filled, singly occupied molecular orbital in AAA molecules, and for a corresponding half-filled band in [A]_infinity chains. 3) The vibronic stability on an AAA molecle increases with a decrease of the AA bond length, as does the vibronic stability of [A]_infinity chains (external pressure may lead to a reversal of a Peierls distortion). 4) The high degree of s-p mixing and ionic/covalent fobriden curve crossing dramatically enhance the vibronic instability of both AAA introduce one quantitative relationship: The parameter log(R) where R is molar refractivity, a parameter used by Herz-feld to prescribe the conditions for the metallization of the elements) correlates with a parameter f_AA (defined as twice the electrongativity of A, divided by the equilibrium AA bond length), used by two of us previously to describe vibronic coupling in AAA molecules for a broad range of elements (A = halogen H, or an alkali metal). We hope to illustrate that key chemical aspects of vibronic coupling in simple molecules may thus be profitably transferred to corresponding materials in the solid state.
机译：我们将先前在简单的同核和异核分子中“振动耦合化学”研究中获得的经验总结出来，以开始为构建具有大电子-声子耦合能力的潜在超导固体组装理论指导。为此，我们分析了分离的分子和扩展的固体中的电子耦合之间的相似性。特别是，我们研究了沿线性对称AAA分子的反对称拉伸坐标（Q_as），以及沿等距A原子构成的相应一维[A] _infinity链的光子“配对”模式坐标（Q_opt）的振动耦合。 。可以对多种化学元素（A）进行此操作。由我们的计算得出，分子中的电子耦合与固体中的声子耦合之间存在以下相似性：1）AAA分子中的HOMO / LUMO电子能隙沿Q_as增大，并且在[A]中占据最高的晶体轨道/最低的未占据晶体轨道间隙] _infinity链沿Q_opt增加。 2）对于AAA分子中的半填充，单个占据的分子轨道以及[A] _无限链中相应的半填充带，总是获得最大的电子振动不稳定性。 3）AAA分子上的电子稳定性随AA键长度的减少而增加，[A] _无穷链的电子稳定性也一样（外部压力可能会导致Peierls变形的逆转）。 4）高度的sp混合和离子/共价fobriden曲线交叉极大地增强了两种AAA的振动电子不稳定性，引入了一种定量关系：参数log（R），其中R为摩尔折射率，Herz-feld使用该参数来规定元素金属化的条件）与参数f_AA（定义为A的两倍，除以平衡的AA键长）相关的参数f_AA，先前我们两个人用来描述AAA分子中各种元素的振动耦合（A =卤素H或碱金属）。我们希望说明简单分子中的振动耦合的关键化学方面因此可以有利地转移到固态的相应材料中。

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