Development of Divide-and-Conquer Quantum Chemical Code for Biomolecules and Nano Materials

Straightforward applications of standard quantum chemical methods to biomolecules and nano materials are essentially impossible because of the undesired computational time required for the calculations, scaling at least cubically with the system size N. Up to now, many types of accelerating techniques for the quantum chemical calculations, which reduce the complexity to O(N), have been developed. The divide-andconquer (DC) quantum chemical method firstly proposed by Yang and Lee [1] is a pioneering method that diminishes the computational cost for the Hartree–Fock (HF) and density functional theory (DFT) calculations. The authors and coworkers have extended the DC method to the post-HF electron correlation calculations (e.g., the second-order Møller– Plesset (MP2) theory [2]) with the help of the energy density analysis (EDA) [3]. In 2009, they released the DC quantum chemistry program as a part of GAMESS package [4]. The DCbased O(N) methods are summarized in the review articles [5,6] In this Paper, we present recent developments in the DC method and show their applications to biomolecules and nano materials.