We have been developing the ABINIT-MP program for the fragment molecular orbital (FMO) method. The list of inter-fragment interaction energies (IFIEs) is available from FMO calculations and is useful in analyzing the nature of interactions in a given target system. In this Letter, we summarize the current status of ABINIT-MP and also the machine-learning assisted analyses of IFIE data.
In this article, a new index was developed for predicting the band gap of π-conjugated polymers based on isodesmic reactions between a dimethylated monomer and an oligo-acetylene. The index can be uniquely defined for hetero-cyclic and poly-cyclic monomers. The index correlated well with the calculated band gap of polymers. In addition, it shows that band gap can be controlled by copolymerization using the index based on only monomer information without calculations of polymers.
Recently, simulations with coarse-graining models, such as coarse-grained molecular dynamics (CG-MD) and dissipative particle dynamics (DPD), have attracted practical interest. We have developed a portable code CAMUS for DPD simulations. Performance evaluations of CAMUS (Code for dissipative particle dynAMics simUlationS) have been made by comparison with COGNAC (Coarse-Grained molecular dynamics program by Nagoya Cooperation) as a standard DPD code, in 5,000 − 100,000 particles systems.
Mullite has a complicated crystal structure in which double occupancy of metal atoms and oxygen vacancies take a random arrangement．Various attempts have been made to describe its structure，but it has not yet been fully described．The purpose of this study is to clarify that the random arrangement has regularity. Excluding arbitrariness，the arrangement of metal atoms and oxygen vacancies of mullite crystals of three compositions (1.58Al2O3，1.75Al2O3，1.95Al2O3 for 1SiO2) was randomly generated．Structural relaxation calculations of these models were performed，and their stability was examined．The wide distribution of the heat of formation obtained by the structural relaxation calculation was consistent with the composition．
Organic reactions with fullerene realize functional nanomaterials, although selective functionalization is still challenging because of many equivalent olefins causing various regioisomers. Thus, the improvement of reactivity and regioselectivity of C60 reaction has been realized by structural organic chemistry such as enhancement of strain, introduction of heteroatom, and nucleophilic additoin via single eletron transfer (Figure 1 Figure 1. Concept of the activation of C60 to obtain regioselective adducts. ). This paper presents the theoretical clarification for the reactivity and selectivity of these activated reaction conditions.
A simple model of localized electron wave packets, floating and breathing Gaussians with non-orthogonal valence-bond spin-coupling, is demonstrated to produce an accurate high-harmonic generation (HHG) spectrum from an LiH molecule induced by an intense laser pulse. In contrast with the conventional molecular orbital picture in which the Li 2s and H 1s atomic orbitals are strongly mixed in the valence σ bonding orbital, the present calculation indicates that a superposition of independent responses of the electrons reproduces the spectrum in which the contribution of the H 1s electron dominates the characteristic plateau and cut-off of HHG.
We propose a unique strategy based on the dimensionality of anionic electrons for new inorganic electride search. We adopted strontium phosphide as the initiator for the evolutionary search, and our evolutionary calculations combined with experimental synthesis found the Sr5P3 is a new one-dimensional electride.
Since the appearance of bulk heterostructures, organic thin film solar cells have attracted attention as next-generation energy sources. Earlier studies have addressed quantum chemical calculation in an excited state and a ground state of phthalocyanine–fullerene bimolecular systems. Phthalocyanines and fullerenes are well known as materials of organic thin film solar cells. Based on these reports, we have devised a new method of manufacturing organic thin film solar cells and have prepared a device incorporating those features. Nevertheless, the device is so soft that it is considered necessary to strengthen the device by incorporating a fibrous substance. This study investigated the effects on its electronic properties of incorporating molecules like nylon 6 into phthalocyanine using quantum chemical calculation. Results demonstrate partial defects in the electron cloud of phthalocyanine molecules, revealing the occurrence of positive holes. These electron cloud defects result from interaction between nylon dimer molecules and phthalocyanine molecules.
Recently, renewable energy is attracting attention globally. In Japan today, there is a shift with growing momentum to photovoltaic power generation from thermal power generation, which has heretofore served as the foundation of electrical power generation. We are studying improvement of the photovoltaic conversion efficiency of bulk heterojunction organic thin film solar cells and are preparing a device that requires detailed elucidation of its electronic properties and its mechanism of power generation. Accordingly, we have conducted quantum chemical calculations using a molecular pair of phthalocyanine and fullerene C60 employed as a specimen. Specifically, we have computed charge densities and electron clouds in the ground state while varying the molecular distance to 12 Å and 24 Å using the density functional method. Results demonstrate quite high negative charge density in C atoms near phthalocyanine in C60 when the distance between the two molecules is decreased to 12 Å, with a positive charge density in C atoms on the opposite side of phthalocyanine in C60. Results suggest that many conduction electrons and positive holes, the so-called carriers, are generated in the phthalocyanine − fullerene C60 bimolecular system when the molecular distance is decreased to 12 Å.