This paper applies a density functional theory （DFT） and grand canonical Monte Carlo simulations （GCMC） to investigate the physisorptions of molecular hydrogen in single-walled BC3 nanotubes and carbon nanotubes. ...This paper applies a density functional theory （DFT） and grand canonical Monte Carlo simulations （GCMC） to investigate the physisorptions of molecular hydrogen in single-walled BC3 nanotubes and carbon nanotubes. The DFT calculations may provide useful information about the nature of hydrogen adsorption and physisorption energies in selected adsorption sites of these two nanotubes. Furthermore, the GCMC simulations can reproduce their storage capacity by calculating the weight percentage of the adsorbed molecular hydrogen under different conditions. The present results have shown that with both computational methods, the hydrogen storage capacity of BC3 nanotubes is superior to that of carbon nanotubes. The reasons causing different behaviour of hydrogen storage in these two nanotubes are explained by using their contour plots of electron density and charge-density difference.展开更多
采用组合的量子化学ONIOM(our own n-layered integrated molecule orbit and molecule mechanics)(B3LYP/6-31++G(d,p):UFF)方法,研究了限域在SWBNNT(9,9)内α-丙氨酸的分子结构和手性转变通道.为得到高水平的能量,在ONIOM(B3LYP/6-311...采用组合的量子化学ONIOM(our own n-layered integrated molecule orbit and molecule mechanics)(B3LYP/6-31++G(d,p):UFF)方法,研究了限域在SWBNNT(9,9)内α-丙氨酸的分子结构和手性转变通道.为得到高水平的能量,在ONIOM(B3LYP/6-311++G(3df,3pd):UFF)水平,计算了各个包结物的单点能.分子结构分析表明:与单体α-丙氨酸相比,受限在SWBNNT(9,9)内时,骨架碳氮原子间的键长不同程度地缩短,骨架碳原子的键角及骨架碳氮原子的二面角略有增大.反应路径研究发现:α-丙氨酸分子在SWBNNT(9,9)内的手性转变有两条同单体情况大致相同的反应通道,不存在单体情况的含有羰基H和甲基H协同转移过程的反应通道.手性转变反应过程的势能面计算发现:与单体α-丙氨酸手性转变反应过程的主要能垒相比较,在纸外面的氢从手性碳直接到羰基氧的过渡态产生的能垒,从326.5kJ·mol-1降到319.7kJ·mol-1;氢首先在羧基内转移,而后手性碳的氢在纸面外转移到羰基,这两个过程的能垒从198.0kJ·mol-1和320.3kJ·mol-1降到135.5kJ·mol-1和302.7kJ·mol-1.结果表明:限域在SWBNNT(9,9)内的α-丙氨酸,其手性转变过程中不同的氢转移反应能垒被不同程度地降低.展开更多
用量子力学与分子力学组合的ONIOM(MP2/6-311++G(3df,3pd):UFF)//ONIOM(CAM-B3LYP/6-31+G(d,p):UFF)方法,研究了标题反应的机理.分子结构计算表明:Sα-Ala·2H2O@SWCNT(8,8)和Sα-Ala·3H2O@SWCNT(8,8)中,季碳与其上面氢的键长...用量子力学与分子力学组合的ONIOM(MP2/6-311++G(3df,3pd):UFF)//ONIOM(CAM-B3LYP/6-31+G(d,p):UFF)方法,研究了标题反应的机理.分子结构计算表明:Sα-Ala·2H2O@SWCNT(8,8)和Sα-Ala·3H2O@SWCNT(8,8)中,季碳与其上面氢的键长分别是0.11055和0.11100(nm),比Sα-Ala·1H2O@SWCNT(8,8)的季碳与其上面氢的键长0.10991nm明显长;环形过渡态TS1·2H2O@SWCNT(8,8)和TS1·3H2O@SWCNT(8,8)的氢键键角比TS1·1H2O@SWCNT(8,8)的明显增大.势能面计算发现:在SWCNT(8,8)内以1个、2个和3个H2O分子为氢转移媒介,α-Ala的质子从季碳向羰基氧迁移的能垒是208.6、160.9和154.4(k J·mol-1).比α-Ala限域在SWCNT(8,8)内质子从季碳向羰基氧迁移的能垒322.7 k J·mol-1大幅降低.结果表明:SWCNT(8,8)与水的复合环境对α-Ala的质子从季碳向羰基氧迁移具有较好的催化作用.展开更多
基金Project supported by Henan University of Technology Foundation (Grant No. 2009BS025)China Academy of Engineering Physics Foundation (Grant No. 2007B08008)
文摘This paper applies a density functional theory （DFT） and grand canonical Monte Carlo simulations （GCMC） to investigate the physisorptions of molecular hydrogen in single-walled BC3 nanotubes and carbon nanotubes. The DFT calculations may provide useful information about the nature of hydrogen adsorption and physisorption energies in selected adsorption sites of these two nanotubes. Furthermore, the GCMC simulations can reproduce their storage capacity by calculating the weight percentage of the adsorbed molecular hydrogen under different conditions. The present results have shown that with both computational methods, the hydrogen storage capacity of BC3 nanotubes is superior to that of carbon nanotubes. The reasons causing different behaviour of hydrogen storage in these two nanotubes are explained by using their contour plots of electron density and charge-density difference.
文摘采用组合的量子化学ONIOM(our own n-layered integrated molecule orbit and molecule mechanics)(B3LYP/6-31++G(d,p):UFF)方法,研究了限域在SWBNNT(9,9)内α-丙氨酸的分子结构和手性转变通道.为得到高水平的能量,在ONIOM(B3LYP/6-311++G(3df,3pd):UFF)水平,计算了各个包结物的单点能.分子结构分析表明:与单体α-丙氨酸相比,受限在SWBNNT(9,9)内时,骨架碳氮原子间的键长不同程度地缩短,骨架碳原子的键角及骨架碳氮原子的二面角略有增大.反应路径研究发现:α-丙氨酸分子在SWBNNT(9,9)内的手性转变有两条同单体情况大致相同的反应通道,不存在单体情况的含有羰基H和甲基H协同转移过程的反应通道.手性转变反应过程的势能面计算发现:与单体α-丙氨酸手性转变反应过程的主要能垒相比较,在纸外面的氢从手性碳直接到羰基氧的过渡态产生的能垒,从326.5kJ·mol-1降到319.7kJ·mol-1;氢首先在羧基内转移,而后手性碳的氢在纸面外转移到羰基,这两个过程的能垒从198.0kJ·mol-1和320.3kJ·mol-1降到135.5kJ·mol-1和302.7kJ·mol-1.结果表明:限域在SWBNNT(9,9)内的α-丙氨酸,其手性转变过程中不同的氢转移反应能垒被不同程度地降低.
文摘用量子力学与分子力学组合的ONIOM(MP2/6-311++G(3df,3pd):UFF)//ONIOM(CAM-B3LYP/6-31+G(d,p):UFF)方法,研究了标题反应的机理.分子结构计算表明:Sα-Ala·2H2O@SWCNT(8,8)和Sα-Ala·3H2O@SWCNT(8,8)中,季碳与其上面氢的键长分别是0.11055和0.11100(nm),比Sα-Ala·1H2O@SWCNT(8,8)的季碳与其上面氢的键长0.10991nm明显长;环形过渡态TS1·2H2O@SWCNT(8,8)和TS1·3H2O@SWCNT(8,8)的氢键键角比TS1·1H2O@SWCNT(8,8)的明显增大.势能面计算发现:在SWCNT(8,8)内以1个、2个和3个H2O分子为氢转移媒介,α-Ala的质子从季碳向羰基氧迁移的能垒是208.6、160.9和154.4(k J·mol-1).比α-Ala限域在SWCNT(8,8)内质子从季碳向羰基氧迁移的能垒322.7 k J·mol-1大幅降低.结果表明:SWCNT(8,8)与水的复合环境对α-Ala的质子从季碳向羰基氧迁移具有较好的催化作用.
