We searched for quantum chemical calculations that would properly evaluate strength in the π-electron conjugation of a group of p-phenylethynyl compounds determined by molecular spectroscopy with error ranges. The target molecules are tolane, 1,4-diphenylbutadiyne and 1,4-bis(phenylethynyl)benzene. Quantum chemical calculations were performed with B3LYP, CAM-B3LYP, ωB97X-D, M06-2X, and MP2 for theory, and basis sets were explored among the combinations 6-311++G(d) cc-pVDZ, and aug-cc-pVDZ. Because B3LYP calculation is considered to be unskilled at evaluating dispersion force, a dispersion force correction term is added to B3LYP calculation. The least of square of the difference in the strength between observed and calculated was given by calculations with M06-2X/aug-cc-pVDZ. It has, however, often been reported that M06-2X undergoes inappropriate structural optimization. In calculations for 1,4-diphenylbutadiyne, M06-2X was not giving systematic uniform results. Overall, ωB97X-D was a functional function corrected for long-range and dispersion force correction, and it was considered to give good results together with CAM-B3LYP corrected for dispersion force.

In August 2023, we released the latest version of our ABINIT-MP program, Open Version 2 Revision 8. In this version, the most commonly used FMO-MP2 calculations are even faster than in the previous Revision 4. It is now also possible to calculate excitation and ionization energies for regions of interest. Improved interaction analysis is also available. In addition, we have started GPU-oriented modifications. In this preliminary report, we present the current status of ABINIT-MP.

Organic thin-film solar cells, which have attracted attention as a renewable energy source in recent years, provide important benefits of being light weight, flexible, inexpensive, and produced from a virtually inexhaustible resource. This report explains the power generation principle of organic thin-film solar cells by particularly addressing the movement of conduction electrons and holes, based on knowledge introduced in a paper and letters presented at this conference, augmented with findings from the calculation results reported here. The following important findings must be considered. (1) Regarding the bimolecular system of phthalocyanine and fullerene C₆₀, even in the configuration calculated for this study, some parts of the phthalocyanine molecule had low probability of electron cloud existence. (2) For this configuration, a change was found in the electronic state in the excited state compared to the ground state. The power generation mechanism of organic thin-film solar cells was considered from the carrier perspective.

The Hartree-Fock-Slater (HFS) equation including magnetic interaction was solved full-numerically by the LCAO-MO method. Firstly, the AOs of each atom in a molecule were obtained by solving the HFS equation dedicated to the atom. This equation includes the same magnetic interaction as the equation of the molecule and virtual "well potential" to adjust the spreads of AOs. In this method, the Fock operator for the atom is expressed as a numerical matrix and the equation can be solved by a mathematical solver of the numerical eigenvalue problem. Then an MO is obtained by using these AOs as bases of the LCAO-MO method. AOs naturally have suitable complex phases for the MO to satisfy gauge invariance. To evaluate the new method, magnetic shielding constants σ were calculated for various small molecules comprising 2-3 atoms of second-row element and hydrogen atoms. The "well potential" of each atom was adjusted systematically and calculated σ showed fairly good agreement with experimental values.

Information about molecular adsorption strength is important in every catalytic reaction. The ability to compare and determine relevant molecular active sites of interaction is necessary for fast screening of potential catalysts specially in a vast spectrum of probable candidates. In this study, we used the metal-coordination of the adsorption sites as a descriptor of the adsorption energy of CO on the PtRuIr ternary alloy nanoparticle. Using multiple regression model, we are able to predict the adsorption energy and specify some important descriptors that controls the strength of CO adsorption energy. This will enable a fast prediction of CO adsorption energy on PtRuIr nanoparticles with varying compositions and possible different morphologies using only the information of the structure of the catalyst. And open up the possibility of predicting adsorption interaction of other combinations of alloys with higher number of metallic compositions for fast screening of appropriate molecule-surface interaction.

This paper describes a method for calculating the intrinsic e parameter of initiator radicals by applying the intrinsic Q-e scheme to the addition reaction between initiator radicals and monomers. Furthermore, DFT calculations show that there is a good relationship between the intrinsic e-value of initiator radicals and their electronegativity and Hammett constant, indicating that the e-value is a suitable parameter to describe the polar effect of initiator radicals.

The experimental mobilities of organic semiconductors, 2-C_n-BTNT (Figure 1), depend on the alkyl chain length n, while the mechanism is unclear. In this study, we elucidate the relationship between alkyl chain length and carrier mobility by classical force field (FF) and density functional theory (DFT) calculations. We analyzed the interactions between an alkyl chain and surrounding molecules and executed NVT molecular dynamics simulations at room temperature and ambient pressure by FF calculations. Transfer integrals were calculated using the DFT method with the coordinates after NVT simulations. As a result, alkyl chain length affects the lattice constant, thermal motion of the alkyl chain and transfer integrals and gives the difference of mobilities.

C–H activation using transition metal catalysts is one of the hot topics in organic chemistry because of their high catalytic reactivities. In this study, we aim to theoretically reveal the mechanism of deuteration of 8-methylquinoline, which shows regioselectivity depending on metal species and ligands used in the catalysts. This report shows the results of analysis in the step of oxidative addition from a viewpoint of relativistic effects.

A reaction route map (RRM), which is a collection of elementary reaction pathways, contracts the potential energy surface (PES) with 3N − 6 variables (N: the number of atoms) into a weighted graph representation. Although the automated construction of RRMs has greatly contributed to the accurate understanding of chemical reaction mechanisms, only a small fraction of networks with low activation energies are relevant to actual chemical reactions, and thus studies focusing on the entire RRM have not been conducted. In this letter, we summarize our recent approach to applying the persistent homology (PH) analysis to the graph structure of an RRM.

Circularly polarized luminescence (CPL) materials have the potential for application in advanced optical devices. Oxaza[7]dehydrohelicene is a helicene-like organic molecule exhibiting CPL property for which an efficient synthesis method has been established. Although the correlation between circular dichroism (CD) and CPL for helicene systems is known and utilized for the screening of CPL materials, it is unclear whether the correlation exists for oxaza[7]dehydrohelicene derivatives. In this study, we conducted a comprehensive calculation of CD and CPL for up to three-substituted oxaza[7]dehydrohelicene derivatives. Numerical results demonstrated that the correlation between CD and CPL decreases as the molecule becomes more complex. The changes in the orbital distribution of S₀ and S₁ optimized structures lead to the gap between CD and CPL.

While Sn-based perovskite solar cells have photoelectronic properties comparable to those of lead halide perovskites, their low photoelectric conversion efficiency is a problem. The main cause of this problem is the defect level caused by the presence of defects in the crystal. In this study, we analyzed the defect structures in FASnI₃ and MASnI₃ perovskites using first-principles calculations and focused on the correlation between the photoelectric conversion efficiency and defect levels.

In both structures, the defect formation energy of V_Sn was low and tin tended to be easily removed. In FASnI₃, by changing the chemical potential to the Sn-rich, I-poor condition, the defect levels that were easy to form in the Sn-poor, I-rich condition became defect levels that were hard to form. It was also found that MASnI₃ has a wide range of thermodynamically stable regions with no defect levels that are prone to form under any chemical potential condition. Therefore, from the viewpoint of structural stability and structural defects, MA is preferable to FA as the A-site cation of Sn-based perovskite.