The goal of this brief partly review paper is to summarize the results of the works published over the last few years regarding the origin of the out-of-plane distortions (puckering) of heterocyclic compounds. In all ...The goal of this brief partly review paper is to summarize the results of the works published over the last few years regarding the origin of the out-of-plane distortions (puckering) of heterocyclic compounds. In all the papers devoted to this problem, it is shown that the instability of planar configurations of heterocyclic molecules leading to symmetry breaking and distortions is induced by the pseudo Jahn-Teller effect (PJTE). Special attention in this work is paid to the mechanism of suppression and enhancement of the PJTE distortions of heterocycles by oxidation, reduction, and chemical substitutions. It is demonstrated that oxidation of 1,4-dithiine containing compounds leads to suppression of the PJTE and to restoration of their planar nuclear configurations. An example of a dibenzo[1,2]dithiine molecule is used to demonstrate the mechanism of enhancement of the PJTE by reduction. It is shown that the reduction of the neutral C12H8S2 molecule up to the dianion (C12H8S2)2- enhances the PJTE, followed by the S-S bond cleavage and significant structural distortions of the system. The change of the PJTE by chemical substitutions, accompanied either by puckering or by planarization of heterocyclic compounds, is discussed using as examples 1,4-ditinine and its S-oxygenated derivatives.展开更多
This paper reports on a computational model established based on discriminant analysis for predicting the occur-rence of seam pucker and advising on the correction of causing variables (e. g. fabric properties) to pre...This paper reports on a computational model established based on discriminant analysis for predicting the occur-rence of seam pucker and advising on the correction of causing variables (e. g. fabric properties) to prevent seam pucker. The model has a self - updating feature, viz. automatically up - dating model parameters to im-prove the reliability of the model as new data becomes available. It has been successfully implemented in a re-cently developed sewability system.展开更多
Two-dimensional(2D)magnetic crystals have been extensively explored thanks to their potential applications in spintronics,valleytronics,and topological superconductivity.Here we report a novel monolayer magnet,namely ...Two-dimensional(2D)magnetic crystals have been extensively explored thanks to their potential applications in spintronics,valleytronics,and topological superconductivity.Here we report a novel monolayer magnet,namely puckered pentagonal VTe_(2)(PP-VTe_(2)),intriguing atomic and electronic structures of which were firmly validated from first-principles calculations.The PP-VTe_(2) exhibits strong intrinsic ferromagnetism and semiconducting property distinct from the half-metallic bulk pyrite VTe_(2)(BP-VTe_(2))phase.An unusual magnetic anisotropy with large magnetic exchange energies is found.More interestingly,the multiferroic coupling between its 2D ferroelasticity and in-plane magnetization is further identified in PP-VTe_(2),lending it unprecedented controllability with external strains and electric fields.Serving as an emergent 2D ferromagnetic semiconductor with a novel crystal structure,monolayer PP-VTe_(2) provides an ideal platform for exploring exotic crystalline and spin configurations in low-dimensional systems.展开更多
文摘The goal of this brief partly review paper is to summarize the results of the works published over the last few years regarding the origin of the out-of-plane distortions (puckering) of heterocyclic compounds. In all the papers devoted to this problem, it is shown that the instability of planar configurations of heterocyclic molecules leading to symmetry breaking and distortions is induced by the pseudo Jahn-Teller effect (PJTE). Special attention in this work is paid to the mechanism of suppression and enhancement of the PJTE distortions of heterocycles by oxidation, reduction, and chemical substitutions. It is demonstrated that oxidation of 1,4-dithiine containing compounds leads to suppression of the PJTE and to restoration of their planar nuclear configurations. An example of a dibenzo[1,2]dithiine molecule is used to demonstrate the mechanism of enhancement of the PJTE by reduction. It is shown that the reduction of the neutral C12H8S2 molecule up to the dianion (C12H8S2)2- enhances the PJTE, followed by the S-S bond cleavage and significant structural distortions of the system. The change of the PJTE by chemical substitutions, accompanied either by puckering or by planarization of heterocyclic compounds, is discussed using as examples 1,4-ditinine and its S-oxygenated derivatives.
文摘This paper reports on a computational model established based on discriminant analysis for predicting the occur-rence of seam pucker and advising on the correction of causing variables (e. g. fabric properties) to prevent seam pucker. The model has a self - updating feature, viz. automatically up - dating model parameters to im-prove the reliability of the model as new data becomes available. It has been successfully implemented in a re-cently developed sewability system.
基金supported by the National Key Research and Development Program of China(Nos.2020YFA0308800,2016YFA0202300,and 2016YFA0300902)the National Natural Science Foundation of China(Nos.91850120 and 11974045)the Strategic Priority Research Program(B)of CAS(No.XDB30000000)。
文摘Two-dimensional(2D)magnetic crystals have been extensively explored thanks to their potential applications in spintronics,valleytronics,and topological superconductivity.Here we report a novel monolayer magnet,namely puckered pentagonal VTe_(2)(PP-VTe_(2)),intriguing atomic and electronic structures of which were firmly validated from first-principles calculations.The PP-VTe_(2) exhibits strong intrinsic ferromagnetism and semiconducting property distinct from the half-metallic bulk pyrite VTe_(2)(BP-VTe_(2))phase.An unusual magnetic anisotropy with large magnetic exchange energies is found.More interestingly,the multiferroic coupling between its 2D ferroelasticity and in-plane magnetization is further identified in PP-VTe_(2),lending it unprecedented controllability with external strains and electric fields.Serving as an emergent 2D ferromagnetic semiconductor with a novel crystal structure,monolayer PP-VTe_(2) provides an ideal platform for exploring exotic crystalline and spin configurations in low-dimensional systems.
