First-principles study on the intermediate compounds of LiBH4_4

We report the results of the first-principles calculation on the intermediate compounds of LiBH$_4$. The stability of LiB$_3$H$_8$ and Li$_2$B$_n$H$_n (n=5-12)$ has been examined with the ultrasoft pseudopotential method based on the density functional theory. Theoretical prediction has suggested that monoclinic Li$_2$B$_{12}$H$_{12}$ is the most stable among the candidate materials. We propose the following hydriding/dehydriding process of LiBH$_4$ via this intermediate compound : LiBH$_4 \leftrightarrow {1/12}$Li$_{2}$B$_{12}$H$_{12} + {5/6}$ LiH $+ {13/12}$H$_2 \leftrightarrow$LiH $+$ B $+ {3/2}$H$_2$. The hydrogen content and enthalpy of the first reaction are estimated to be 10 mass% and 56 kJ/mol H$_2$, respectively, and those of the second reaction are 4 mass% and 125 kJ/mol H$_2$. They are in good agreement with experimental results of the thermal desorption spectra of LiBH$_4$. Our calculation has predicted that the bending modes for the $\Gamma$-phonon frequencies of monoclinic Li$_2$B$_{12}$H$_{12}$ are lower than that of LiBH$_4$, while stretching modes are higher. These results are very useful for the experimental search and identification of possible intermediate compounds.Comment: 7 pages, 5 figures, submitted to PR

Developing Lesson Modules for Reconstruction of Perspectives on Peace and Meta-cognition of its Process

The aim of this study is to develop the module for peace education which helps learners to reconstruct their own perspectives on peace. Previous studies introducing lesson plans on peace education have limitation in that these lesson plans focus heavily on wars or issues unfamiliar to students. In addition, they were not intended to give opportunities to metacognize the reconstruction of perspectives on peace. The lesson module we developed consists of three section: introduction section, main section, closing section. The main section consists of six units, and we chose six concepts or theories with which learners reconstruct their perspectives on peace：(1)game theory, (2)Galtung’s theory of peace, (3)conflict resolution, (4)authoritarian personality, (5)labeling theory, and, (6)social identity. This lesson module includes not only various concepts or theories about peace but also the process through which learners reconstruct their own perspectives on peace and reflection on the process in order to cultivate peace-makers

The method of lesson study based on the structure of the subject: the case of primary social studies classroom

This study presents the case study of the lesson study in a primary social studies classroom in Japan. The result indicates to propose a new method of social studies lesson study. While previous method tended to pay less attention to the context of school and children because of the focus of generalization, this study highlights the reality of diverse children in a classroom settings. Throughout the study, we compared the two items: The structure of the subject, namely, triangle relation of goals, contents, and methods and learner 's learning structure. Comparing the two items, we could see the effect of the process of teaching and learning on the children. It means that we can propose the new method by focusing on the reality of the classroom

Development of Hydrogen-Bonded Dimer-Type Photoluminescent Liquid Crystals of Fluorinated Tolanecarboxylic Acid

Functional molecules possessing photoluminescence (PL) and liquid-crystalline (LC) behaviors, known as photoluminescent liquid crystals, along with a small molecular structure, have attracted significant attention. Fluorinated tolane skeletons are small π-conjugated structures, which are promising candidates for such functional molecules. These structures were revealed to exhibit strong PL in solid state but no LC behavior. Based on a report on hydrogen-bonded dimer-type LC molecules of carboxylic acid, in this study, we designed and synthesized a series of fluorinated tolanecarboxylic acids (2,3,5,6-tetrafluoro-4-[2-(4-alkoxyphenyl)ethyn-1-yl]benzoic acids) as promising PLLC molecules. Evaluation of the LC behavior revealed that fluorinated tolanecarboxylic acids with a longer alkoxy chain than a butoxy chain exhibited nematic LC behavior. Additionally, fluorinated tolanecarboxylic acids showed intense PL in the solution and crystalline states. Notably, fluorinated tolanecarboxylic acid with an aggregated structure in the nematic LC phase also exhibited PL with a slight blue shift in PL maximum wavelength compared to the crystalline state. The present fluorinated tolanecarboxylic acid exhibiting PL and LC characteristics in a single molecule can be applied to thermoresponsive PL materials, such as a PL thermosensor

Effect of fluoroalkyl-substituent in bistolane-based photoluminescence liquid crystals on their physical behavior

Funding: This research was funded by JSPS KAKENHI through a Grant-in-Aid for Scientific Research (C), grant number JP18K05262.Photoluminescentliquid crystals (PLLCs) have attracted significant attention owing to their broad applicabilityin thermosensing and PL switching. Extensive efforts have been madeto develop bistolane-based PLLCs containing flexible units at both molecular terminals, and it has been revealed that their PL behavior can switch with the phase transition between the crystallineand LC phases. Although slight modulation of the flexible unit structure dramatically alters the LC and PL behaviors, few studies into modification of the flexible units have been conducted. With the aim of achieving dynamic changes in their physical behaviors, we developed a family of bistolane derivatives containing a simple alkyl or a fluoroalkyl flexible chain, and carried out a detailed systematic evaluationof their physical behaviors. Bistolanes containing a simple alkyl chain showed a nematic LC phase, whereas switching the flexible chain in the bistolane to a fluoroalkyl moiety significantly altered the phase to generate a smectic phase. The fluoroalkyl-containing bistolanes displayed a stronger deep blue PL than their corresponding non-fluorinated counterparts, even in the crystalline phase, which was attributed to the construction of rigid molecular aggregates through intermolecular F···H and F···F interactions to suppress non-radiative deactivation.Publisher PDFPeer reviewe