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Tetrathiafulvalene-p-chloranil exhibits photoinduced phase transition (PIPT) between neutral (N) and ionic (I) phases, in which the constituent molecules are approximately charge-neutral and ionic, respectively. In addition to visible-light irradiation, which can induce both N → I and I → N PIPTs, infrared irradiation has been reported to induce the N → I PIPT. These results suggest that N → I and I → N PIPTs can be driven by electronic excitation, and the I → N PIPT can also be driven by vibrational excitation. However, the feasibility of the N → I PIPT using vibrational excitation remains an open question. In this study, we address this issue by simulating the PIPT processes using a nonadiabatic molecular dynamics approach combined with real-time electron dynamics at the level of a semiempirical quantum chemical model, density-functional tight binding. The results show the importance of vibronic interactions in the PIPT processes, thereby suggesting the possibility of N → I PIPT by vibrational excitations with infrared irradiation. [ABSTRACT FROM AUTHOR]

Many of the non-adiabatic processes in the condensed phase are affected by the interaction with the environment, as exemplified by Marcus theory. However, non-adiabatic molecular dynamics simulations with explicitly including the environment are computationally expensive because of the extended system size, suggesting the need for an efficient scheme applicable to huge systems. In this work, time-derivative non-adiabatic coupling (TDNAC) calculation algorithms were developed in the framework of the divide-and-conquer (DC) time-dependent (TD) density-functional tight-binding (DFTB) method, which is an extension of the TD-DFTB for larger systems based on the fragmentation-based DC scheme. The developed algorithms were incorporated into a fewest-switches trajectory surface hopping (FSSH) routine. The calculated TDNAC and the FSSH results were sufficiently accurate compared to the conventional TD-DFTB results. Use of the DC-TD-DFTB provided a significant reduction in the central processing unit (CPU) time vs that of the TD-DFTB, where the CPU time remained constant irrespective of the total system size. It was also confirmed that the present method is not only efficient but also improves the numerical stability of TDNAC calculations. [ABSTRACT FROM AUTHOR]

We fabricated n-channel MOSFETs with various gate dielectrics on (111) oriented 3C-SiC/Si. Fabricated MOSFETs operated as inversion mode devices successfully. The MOSFET with sputter-deposited SiO2/plasma oxidized interlayer showed a high peak field-effect mobility of 131 cm2 Vâˆ'1 sâˆ'1. The gate stack can be formed at a low temperature of 400 °C, which means the process is absolved from high-temperature thermal oxidation for a gate stack. The detailed analysis of charges and traps in the gate stacks clarified that Coulomb scattering is well-suppressed in the inversion channel. These results will be the first step for a high-performance 3C-SiC application, including on-chip hetero-integrated electronic devices. [ABSTRACT FROM AUTHOR]

We investigated the atomistic and dynamical mechanism of polaron formation in methylammonium lead iodide perovskite (MAPbI3), which is a representative perovskite solar cell absorber, through the quantum mechanical molecular dynamics simulations. The simulations were conducted on the spatial scale of several nanometres, which can describe charge localization and the associated structural deformation, using the divide-and-conquer-type density-functional tight-binding method, which enables a quantum chemical treatment of systems comprising thousands of atoms. We found that both the structural parts of MAPbI3, namely, the inorganic framework (PbI3-) and the MA cations, involve the structural deformation associated with polaron formation. We elucidated that in the process of polaron formation, charge localization is invoked by thermal structural fluctuation, and a further structural deformation is caused by the relaxation of the charge carrier. Finally, importance of the two structural parts, PbI3- and MA, was examined from the energetical viewpoint.

Following natural disasters, accidents, and shocking incidents, some children experience post-traumatic stress disorder (PTSD). The respiration control method, which relaxes the body and mind, may efficiently prevent PTSD. Therefore, we developed a stuffed toy that leads children's respiration using the up-and-down movement of the abdomen to help them relax. We investigated the most appropriate respiration period for children's relaxation. Data from studies on heart rate variability (HRV) biofeedback training suggest that breathing at the respiration period at which HRV is the highest is effective for improving chronic diseases. Therefore, we measured the relationship between the respiration period and physiological indices, including HRV. The participants were 10 children aged 5-12 years. HRV was the highest at a 10-12-s respiration period in all 10 children. However, the most suitable respiration period for smooth breathing and relaxation was different from that at which HRV is the highest. Therefore, the most relaxing respiration periods for children need to be determined by indices other than HRV.