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.