Extension of the self-consistent-charge density-functional tight-binding method: third-order expansion of the density functional theory total energy and introduction of a modified effective coulomb interaction.
Extension of the self-consistent-charge density-functional tight-binding method: third-order expansion of the density functional theory total energy and introduction of a modified effective coulomb interaction.
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DOI：
10.1021/jp074167r
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发表时间：
2007-10
期刊：
影响因子：
--
通讯作者：
Yang Yang-Yang;Haibo Yu;D. York;Q. Cui;M. Elstner
中科院分区：
文献类型：
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作者：
Yang Yang-Yang;Haibo Yu;D. York;Q. Cui;M. Elstner
标准的自洽电荷密度泛函紧束缚（SCC-DFTB）方法（Phys. Rev. B 1998，58，7260）是由密度泛函理论总能量表达式的二阶展开、电荷密度涨落的电荷单极近似和原子净电荷之间的有效阻尼库仑相互作用导出的。这种有效的电荷-电荷相互作用背后的中心假设是原子尺寸和化学硬度的反比关系，以及使用独立于原子电荷状态的固定化学硬度参数。虽然这些近似似乎是没有问题的许多共价键合系统，它们是定量的氢键相互作用和（阴离子）分子与本地化的净电荷不足。在这里，我们提出了一个扩展的SCC-DFTB方法，将三阶项中的电荷密度波动，导致化学硬度参数依赖于原子的电荷状态和修改的库仑缩放，以提高静电处理内的二阶项。这些修改导致在生物相关分子的氢键相互作用和质子亲和力的描述中的显著改进。
The standard self-consistent-charge density-functional-tight-binding (SCC-DFTB) method (Phys. Rev. B 1998, 58, 7260) is derived by a second-order expansion of the density functional theory total energy expression, followed by an approximation of the charge density fluctuations by charge monopoles and an effective damped Coulomb interaction between the atomic net charges. The central assumptions behind this effective charge-charge interaction are the inverse relation of atomic size and chemical hardness and the use of a fixed chemical hardness parameter independent of the atomic charge state. While these approximations seem to be unproblematic for many covalently bound systems, they are quantitatively insufficient for hydrogen-bonding interactions and (anionic) molecules with localized net charges. Here, we present an extension of the SCC-DFTB method to incorporate third-order terms in the charge density fluctuations, leading to chemical hardness parameters that are dependent on the atomic charge state and a modification of the Coulomb scaling to improve the electrostatic treatment within the second-order terms. These modifications lead to a significant improvement in the description of hydrogen-bonding interactions and proton affinities of biologically relevant molecules.