Chulhai Dhabih V, Jensen Lasse
Department of Chemistry, The Pennsylvania State University , 104 Chemistry Building, University Park, Pennsylvania 16802, United States.
J Chem Theory Comput. 2015 Jul 14;11(7):3080-8. doi: 10.1021/acs.jctc.5b00293.
Frozen density embedding (FDE) has become a popular subsystem density functional theory (DFT) method for systems with weakly overlapping charge densities. The failure of this method for strongly interacting and covalent systems is due to the approximate kinetic energy density functional (KEDF), although the need for approximate KEDFs may be eliminated if each subsystem's Kohn-Sham (KS) orbitals are orthogonal to the other, termed external orthogonality (EO). We present an implementation of EO into the FDE framework within the Amsterdam density functional program package, using the level-shift projection operator method. We generalize this method to remove the need for orbital localization schemes and to include multiple subsystems, and we show that the exact KS-DFT energies and densities may be reproduced through iterative freeze-and-thaw cycles for a number of systems, including a charge delocalized benzene molecule starting from atomic subsystems. Finally, we examine the possibility of a truncated basis for systems with and without charge delocalization, and found that subsystems require a basis that allows them to correctly describe the supermolecular delocalized orbitals.
对于电荷密度弱重叠的体系，冷冻密度嵌入（FDE）已成为一种流行的子体系密度泛函理论（DFT）方法。该方法在强相互作用和共价体系中失效是由于近似的动能密度泛函（KEDF），不过，如果每个子体系的Kohn-Sham（KS）轨道与其他轨道正交，即所谓的外部正交性（EO），则可能无需近似的KEDF。我们在阿姆斯特丹密度泛函程序包中，利用能级移动投影算符方法，将EO实现到FDE框架中。我们对该方法进行了推广，以消除对轨道定域化方案的需求并纳入多个子体系，并且我们表明，对于许多体系，包括从原子子体系出发的电荷离域苯分子，通过迭代的冻融循环可以重现精确的KS-DFT能量和密度。最后，我们研究了有电荷离域和无电荷离域体系采用截断基的可能性，发现子体系需要一个能使其正确描述超分子离域轨道的基。
