The potential energy surfaces of CN_(6)O isomers were calculated at the B3LYP/aug-cc-pVDZ level and the key decomposition pathways were calculated at the G3B3 level.The optimum pathway for the decomposition of carbony...The potential energy surfaces of CN_(6)O isomers were calculated at the B3LYP/aug-cc-pVDZ level and the key decomposition pathways were calculated at the G3B3 level.The optimum pathway for the decomposition of carbonyl diazide to OCN_(4)and N2 has a barrier of about 30 kcal mol^(−1).Except for carbonyl diazide,no isomer of CN_(6)O crosses a higher decomposition barrier than 20 kcal mol^(−1).The specific impulse of carbonyl diazide is close to those of RDX(cyclotrimethylene trinitramine),HMX(cyclotetramethylene tetranitramine)and CL-20(hexanitrohexaazaisowurtzitane),and the specific impulses of many other CN_(6)O isomers are greater than that of FTDO([1,2,5]oxadizolo[3,4-4][1,2,3,4]tetrazine-4,6-di-Ndioxide).The CN_(6)O system has a higher combustion temperature than RDX,HMX,CL-20 and FTDO at comparable specific impulses.The detonation velocity and pressure of most of CN_(6)O isomers are lower than that of CL-20.展开更多
The physical origins of the mechanical properties of Fe-rich Si alloys are investigated by combining electronic structure calculations with statistical mechanics means such as the cluster variation method,molecular dy...The physical origins of the mechanical properties of Fe-rich Si alloys are investigated by combining electronic structure calculations with statistical mechanics means such as the cluster variation method,molecular dynamics simulation,etc,applied to homogeneous and heterogeneous systems.Firstly,we examined the elastic properties based on electronic structure calculations in a homogeneous system and attributed the physical origin of the loss of ductility with increasing Si content to the combined effects of magneto-volume and D03 ordering.As a typical example of a heterogeneity forming a microstructure,we focus on grain boundaries,and segregation behavior of Si atoms is studied through high-precision electronic structure calculations.Two kinds of segregation sites are identified:looser and tighter sites.Depending on the site,different segregation mechanisms are revealed.Finally,the dislocation behavior in the Fe-Si alloy is investigated mainly by molecular dynamics simulations combined with electronic structure calculations.The solid-solution hardening and softening are interpreted in terms of two kinds of energy barriers for kink nucleation and migration on a screw dislocation line.Furthermore,the clue to the peculiar work hardening behavior is discussed based on kinetic Monte Carlo simulations by focusing on the preferential selection of slip planes triggered by kink nucleation.展开更多
This work presents an extreme biomimetics route for the creation of nano- structured biocomposites utilizing a chitinous template of poriferan origin. The specific thermal stability of the nanostructured chitinous tem...This work presents an extreme biomimetics route for the creation of nano- structured biocomposites utilizing a chitinous template of poriferan origin. The specific thermal stability of the nanostructured chitinous template allowed for the formation under hydrothermal conditions of a novel germanium oxide- chitin composite with a defined nanoscale structure. Using a variety of analytical techniques （FTIR, Raman, energy dispersive X-ray （EDX）, near-edge X-ray absorption fine structure （NEXAFS）, and photoluminescence （PL） spectroscopy, EDS-mapping, selected area for the electron diffraction pattern （SAEDP）, and transmission electron microscopy （TEM））, we showed that this bioorganic scaffold induces the growth of GeO2 nanocrystals with a narrow （150-300 nm） size distri- bution and predominantly hexagonal phase, demonstrating the chitin template＇s control over the crystal morphology. The formed GeO2-chitin composite showed several specific physical properties, such as a striking enhancement in photo- luminescence exceeding values previously reported in GeOR-based biomaterials. These data demonstrate the potential of extreme biomimetics for developing new-generation nanostructured materials.展开更多
基金partially supported by the National Natural Science Foundation of China(no.51171046,21303133 and 21403162).
文摘The potential energy surfaces of CN_(6)O isomers were calculated at the B3LYP/aug-cc-pVDZ level and the key decomposition pathways were calculated at the G3B3 level.The optimum pathway for the decomposition of carbonyl diazide to OCN_(4)and N2 has a barrier of about 30 kcal mol^(−1).Except for carbonyl diazide,no isomer of CN_(6)O crosses a higher decomposition barrier than 20 kcal mol^(−1).The specific impulse of carbonyl diazide is close to those of RDX(cyclotrimethylene trinitramine),HMX(cyclotetramethylene tetranitramine)and CL-20(hexanitrohexaazaisowurtzitane),and the specific impulses of many other CN_(6)O isomers are greater than that of FTDO([1,2,5]oxadizolo[3,4-4][1,2,3,4]tetrazine-4,6-di-Ndioxide).The CN_(6)O system has a higher combustion temperature than RDX,HMX,CL-20 and FTDO at comparable specific impulses.The detonation velocity and pressure of most of CN_(6)O isomers are lower than that of CL-20.
基金supported by the JST Industry-Academia Collaborative Programs,“Materials Strength from Hamiltonian”,and by the Elements Strategy Initiative for Structural Materials(ESISM)through MEXT,Japansupported by a Grant-in-Aid for Scientific Research on Innovative Area“Bulk Nanostructured Metals”and by the Computational Materials Science Initiative(CMSI),MEXT,Japanthe K computer provided by the RIKEN Advanced Institute for Computational Science through the HPCI System Research project(Project ID:hp130016,hp140233,hp150235).
文摘The physical origins of the mechanical properties of Fe-rich Si alloys are investigated by combining electronic structure calculations with statistical mechanics means such as the cluster variation method,molecular dynamics simulation,etc,applied to homogeneous and heterogeneous systems.Firstly,we examined the elastic properties based on electronic structure calculations in a homogeneous system and attributed the physical origin of the loss of ductility with increasing Si content to the combined effects of magneto-volume and D03 ordering.As a typical example of a heterogeneity forming a microstructure,we focus on grain boundaries,and segregation behavior of Si atoms is studied through high-precision electronic structure calculations.Two kinds of segregation sites are identified:looser and tighter sites.Depending on the site,different segregation mechanisms are revealed.Finally,the dislocation behavior in the Fe-Si alloy is investigated mainly by molecular dynamics simulations combined with electronic structure calculations.The solid-solution hardening and softening are interpreted in terms of two kinds of energy barriers for kink nucleation and migration on a screw dislocation line.Furthermore,the clue to the peculiar work hardening behavior is discussed based on kinetic Monte Carlo simulations by focusing on the preferential selection of slip planes triggered by kink nucleation.
文摘This work presents an extreme biomimetics route for the creation of nano- structured biocomposites utilizing a chitinous template of poriferan origin. The specific thermal stability of the nanostructured chitinous template allowed for the formation under hydrothermal conditions of a novel germanium oxide- chitin composite with a defined nanoscale structure. Using a variety of analytical techniques （FTIR, Raman, energy dispersive X-ray （EDX）, near-edge X-ray absorption fine structure （NEXAFS）, and photoluminescence （PL） spectroscopy, EDS-mapping, selected area for the electron diffraction pattern （SAEDP）, and transmission electron microscopy （TEM））, we showed that this bioorganic scaffold induces the growth of GeO2 nanocrystals with a narrow （150-300 nm） size distri- bution and predominantly hexagonal phase, demonstrating the chitin template＇s control over the crystal morphology. The formed GeO2-chitin composite showed several specific physical properties, such as a striking enhancement in photo- luminescence exceeding values previously reported in GeOR-based biomaterials. These data demonstrate the potential of extreme biomimetics for developing new-generation nanostructured materials.
