设计了一种新型高能量密度化合物2,6-双(二硝基亚甲基)-1,3,4,5,7,8-六硝基十二氢二咪唑[4,5-b:4',5'-e]吡嗪(DNNIP)。首先在B3PW91/6-31G++(d,p)水平下对目标分子进行优化,通过键长和键级的比较分析,判断母环的五元环侧链处N—...设计了一种新型高能量密度化合物2,6-双(二硝基亚甲基)-1,3,4,5,7,8-六硝基十二氢二咪唑[4,5-b:4',5'-e]吡嗪(DNNIP)。首先在B3PW91/6-31G++(d,p)水平下对目标分子进行优化,通过键长和键级的比较分析,判断母环的五元环侧链处N—NO2键为分解引发键,其键解离能是96.40 k J/mol;然后,基于静电势改进的蒙特卡洛法推测出该化合物的理论密度为2.07 g/cm3,采用等键反应计算出生成热为1 907.33 k J/mol,并进一步计算出DNNIP的爆速为10.35 km/s,爆压为51.47 GPa,爆轰性能明显优于现有常见含能材料。DNNIP的撞击感度为12 cm,与CL-20接近;能级差为0.158 78 a.u.(4.32 e V),光热稳定性较高,并且通过态密度分析认为硝基是分子中相对敏感位置。展开更多
Precipitation projections over the Tibetan Plateau(TP)show diversity among existing studies,partly due to model uncertainty.How to develop a reliable projection remains inconclusive.Here,based on the IPCC AR6–assesse...Precipitation projections over the Tibetan Plateau(TP)show diversity among existing studies,partly due to model uncertainty.How to develop a reliable projection remains inconclusive.Here,based on the IPCC AR6–assessed likely range of equilibrium climate sensitivity(ECS)and the climatological precipitation performance,the authors constrain the CMIP6(phase 6 of the Coupled Model Intercomparison Project)model projection of summer precipitation and water availability over the TP.The best estimates of precipitation changes are 0.24,0.25,and 0.45 mm d^(−1)(5.9%,6.1%,and 11.2%)under the Shared Socioeconomic Pathway(SSP)scenarios of SSP1–2.6,SSP2–4.5,and SSP5–8.5 from 2050–2099 relative to 1965–2014,respectively.The corresponding constrained projections of water availability measured by precipitation minus evaporation(P–E)are 0.10,0.09,and 0.22 mm d^(−1)(5.7%,4.9%,and 13.2%),respectively.The increase of precipitation and P–E projected by the high-ECS models,whose ECS values are higher than the upper limit of the likely range,are about 1.7 times larger than those estimated by constrained projections.Spatially,there is a larger increase in precipitation and P–E over the eastern TP,while the western part shows a relatively weak difference in precipitation and a drier trend in P–E.The wetter TP projected by the high-ECS models resulted from both an approximately 1.2–1.4 times stronger hydrological sensitivity and additional warming of 0.6℃–1.2℃ under all three scenarios during 2050–2099.This study emphasizes that selecting climate models with climate sensitivity within the likely range is crucial to reducing the uncertainty in the projection of TP precipitation and water availability changes.展开更多
文摘设计了一种新型高能量密度化合物2,6-双(二硝基亚甲基)-1,3,4,5,7,8-六硝基十二氢二咪唑[4,5-b:4',5'-e]吡嗪(DNNIP)。首先在B3PW91/6-31G++(d,p)水平下对目标分子进行优化,通过键长和键级的比较分析,判断母环的五元环侧链处N—NO2键为分解引发键,其键解离能是96.40 k J/mol;然后,基于静电势改进的蒙特卡洛法推测出该化合物的理论密度为2.07 g/cm3,采用等键反应计算出生成热为1 907.33 k J/mol,并进一步计算出DNNIP的爆速为10.35 km/s,爆压为51.47 GPa,爆轰性能明显优于现有常见含能材料。DNNIP的撞击感度为12 cm,与CL-20接近;能级差为0.158 78 a.u.(4.32 e V),光热稳定性较高,并且通过态密度分析认为硝基是分子中相对敏感位置。
基金supported by the Second Tibetan Plateau Scientific Expedition and Research(STEP)program[grant number 2019QZKK0102]the Chinese Academy of Sciences[grant number 060GJHZ2023079GC].
文摘Precipitation projections over the Tibetan Plateau(TP)show diversity among existing studies,partly due to model uncertainty.How to develop a reliable projection remains inconclusive.Here,based on the IPCC AR6–assessed likely range of equilibrium climate sensitivity(ECS)and the climatological precipitation performance,the authors constrain the CMIP6(phase 6 of the Coupled Model Intercomparison Project)model projection of summer precipitation and water availability over the TP.The best estimates of precipitation changes are 0.24,0.25,and 0.45 mm d^(−1)(5.9%,6.1%,and 11.2%)under the Shared Socioeconomic Pathway(SSP)scenarios of SSP1–2.6,SSP2–4.5,and SSP5–8.5 from 2050–2099 relative to 1965–2014,respectively.The corresponding constrained projections of water availability measured by precipitation minus evaporation(P–E)are 0.10,0.09,and 0.22 mm d^(−1)(5.7%,4.9%,and 13.2%),respectively.The increase of precipitation and P–E projected by the high-ECS models,whose ECS values are higher than the upper limit of the likely range,are about 1.7 times larger than those estimated by constrained projections.Spatially,there is a larger increase in precipitation and P–E over the eastern TP,while the western part shows a relatively weak difference in precipitation and a drier trend in P–E.The wetter TP projected by the high-ECS models resulted from both an approximately 1.2–1.4 times stronger hydrological sensitivity and additional warming of 0.6℃–1.2℃ under all three scenarios during 2050–2099.This study emphasizes that selecting climate models with climate sensitivity within the likely range is crucial to reducing the uncertainty in the projection of TP precipitation and water availability changes.
