It is known for quite some time that approximate density functional (ADF) theories fail disastrously when describing the dis-sociative symmetric radical cations R2+. Considering this dissociation limit, previous work has shown that Hartree-Fock (HF) theory favors the R+1--R0 charge distribution while DF approximations favor the R+0.5 -- R+0.5. Yet, general quantum mechanical principles indicate that both these (as well as all intermediate) average charge distributions are asymptotically energy degenerate. Thus HF and ADF theories mistakenly break the symmetry but in a contradicting way. In this letter we show how to construct system-dependent long-range corrected (LC) density functionals that can successfully treat this class of molecules, avoiding the spurious symmetry breaking. Examples and comparisons to experimental data is given for R=H, He and Ne and it is shown that the new LC theory improves considerably the theoretical description of the R2+ bond properties, the long range form of the asymptotic potential curve as well as the atomic polarizability. The broader impact of this finding is discussed as well and it is argued that the widespread semi-empirical approach which advocates treating the LC parameter as a system-independent parameter is in fact inappropriate under general circumstances.
Free Energy Driven Transfer of Charge in Dense Electrochemically Active Monomolecular Films
对单分子膜作为电导体的兴趣源于对创新材料的探索。非共价键合的膜的效用是有限的，因为它们是机械不稳定的，并由不良连接域。因此，这些膜中的电荷转移被限制在微米量级的距离内。在这里，我们展示了最近开发的气相组装方法（Burtman，V.，Zelichenok，A.，Yitzchaik，S. 04 The Dog of the Dog（1999）Ed.38，2041-2045.），其产生共价连接到硅表面的坚固致密的NTCDI单层，允许人们克服这种规模限制。这些几乎绝缘的单层可以通过将电子喷射到半导体基底中而光化学地填充有阳离子自由基。阳离子自由基的正电荷可以在微秒内以随机游走的方式迁移远达几毫米，从而证明了膜的宏观连通性。由于电荷作为阳离子自由基存在，阳离子自由基是有效的氧化剂，因此它们的迁移与它们还原的自由能的转移相耦合，并且由氧化还原电势梯度驱动。阳离子自由基被阳极还原，将这种自由能转化为电动势。我们展示了这些薄膜如何可以实现在太阳能转换和基本的时间分辨的距离控制的研究序列的超快电子转移。
Post density functional theoretical studies of highly polar semiconductive Pb(Ti$_{1-x}$Ni$_{x}$)O$_{3-x}$ solid solutions: The effects of cation arrangement on band gap
First-principles study of structural, elastic, and bonding properties of pyrochlores
用密度泛函理论计算了组成为A $_2$ B $_2$ O $_7$（其中A=La，Y，B=Ti，Sn，Hf，Zr）的理想辉石的晶格常数、弹性常数和电子性质。还从弹性性质推断了一些热性质。观察到B离子的声速（以及德拜温度）随原子质量的减小而减小。静态和动态的原子电荷获得量化的共价/离子性的程度。一个大的异常贡献的动态电荷观察铪，锆，特别是钛。这归因于氧的占据$2p$态和B阳离子的未占据d态之间的杂化。基于Mulliken布居和变形电荷积分在Voronoi多面体的分析表明，这些辉石的电离度增加的顺序为Sn-Ti-Hf-Zr。电荷变形等值线图支持这一分配。
Confinement of electron holes via the peroxo group formation in the negative charge-transfer materials on the example of SrFeO3: plane-wave density functional theory predictions
