A quantum chemical study from a molecular transport perspective: ionization and electron attachment energies for species often used to fabricate single-molecule junctions
A quantum chemical study from a molecular transport perspective: ionization and electron attachment energies for species often used to fabricate single-molecule junctions
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DOI：
10.1039/c4fd00101j
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发表时间：
2014-01-01
影响因子：
3.4
通讯作者：
Baldea, Ioan
中科院分区：
文献类型：
--
作者：
Baldea, Ioan
准确确定嵌入分子结中的分子的最低电子附着（EA）和电离（UP）能量对于正确估计例如电流（I）的大小或偏置M（其中I-V曲线表现出显著的非欧姆行为）是重要的。用于制备具有n型导电特征的单分子结的几种典型分子的最低电子附着能和电离能的基准计算（4，4 '-联吡啶、1，4-二氰基苯和4，4'-二氰基-1，1 ' -联苯）和p型导电（苯二硫醇，联苯二硫醇，基于EOM-CCSD（equation-of-motion coupled-cluster singles and doubles）量子化学方法，对正己烷单硫醇（hexanemonothiol）和正己烷二硫醇（hexanediothiol）进行了研究。它们表明与目前分子运输方法中获得的结果存在显着差异。本研究强调，除了一个可靠的量子化学方法，基组比无处不在的双zeta设置用于运输计算更好的是必要的。后者对于正确确定EA是一个特别关键的问题，如果不包括足够的扩散基函数，这是不可能的。占主导地位的分子轨道（MO）的空间分布是另一个重要的问题，本研究引起了人们的注意，因为它敏感地影响MO的能量偏移Φ由于图像电荷形成在电极中。目前的结果不能证实电极之间的中点的点状MO的共同假设，这实质上影响实际的Phi值。
The accurate determination of the lowest electron attachment (EA) and ionization UP) energies for molecules embedded in molecular junctions is important for correctly estimating, for example, the magnitude of the currents (I) or the biases M where an I-V curve exhibits significant non-Ohmic behavior. Benchmark calculations for the lowest electron attachment and ionization energies of several typical molecules utilized to fabricate single-molecule junctions characterized by n-type conduction (4,4'-bipyridine, 1,4-dicyanobenzene and 4,4'-dicyano-1,1' -biphenyl) and p-type conduction (benzenedithiol, biphenyldithiol, hexanemonothiol and hexanedithiol) based on the EOM-CCSD (equation-of-motion coupled-cluster singles and doubles) state-of-the-art method of quantum chemistry are presented. They indicate significant differences from the results obtained within current approaches to molecular transport. The present study emphasizes that, in addition to a reliable quantum chemical method, basis sets much better than the ubiquitous double-zeta set employed for transport calculations are needed. The latter is a particularly critical issue for correctly determining EAs, which is impossible without including sufficient diffuse basis functions. The spatial distribution of the dominant molecular orbitals (MOs) is another important issue, on which the present study draws attention, because it sensitively affects the MO energy shifts Phi due to image charges formed in electrodes. The present results cannot substantiate the common assumption of a point-like MO midway between electrodes, which substantially affects the actual Phi-values.