Pedroza Luana S, Silva Anto Nio J R da
Instituto de Física, Universidade de São Paulo, São Paulo, SP, Brazil.
J Chem Phys. 2008 Mar 14;128(10):104311. doi: 10.1063/1.2889952.
An effective treatment of the intramolecular degrees of freedom is presented for water, where these modes are decoupled from the intermolecular ones, "adiabatically" allowing these coordinates to be positioned at their local minimum of the potential energy surface. We perform ab initio Monte Carlo simulations with the configurational energies obtained via density functional theory. We study a water dimer as a prototype system, and even in this simple case the intramolecular relaxations are very important to properly describe properties such as the dipole moment. We show that rigid simulations do not correctly sample the phase space, resulting in an average dipole moment smaller than the one obtained with the adiabatic model, which is closer to the experimental result.
我们提出了一种针对水的分子内自由度的有效处理方法，其中这些模式与分子间模式解耦，“绝热地”使这些坐标位于势能面的局部最小值处。我们通过密度泛函理论获得构型能量，进行从头算蒙特卡罗模拟。我们将水二聚体作为一个原型系统进行研究，即使在这种简单情况下，分子内弛豫对于正确描述诸如偶极矩等性质也非常重要。我们表明，刚性模拟不能正确地对相空间进行采样，导致平均偶极矩小于绝热模型得到的结果，而绝热模型的结果更接近实验结果。
