利用电荷自洽离散变分Xα(SCC-D V-Xα)方法计算了钒基固溶体中钒氢反应前后钒及其氢化物(V H x,x=0,1,2)、假定原子簇模型V H 鄢x(x=1,2)和V H x'(x=0,1)的电子结构.结果表明:钒与氢气反应生成V H 时,化学效应和结构效应都使V 3d和...利用电荷自洽离散变分Xα(SCC-D V-Xα)方法计算了钒基固溶体中钒氢反应前后钒及其氢化物(V H x,x=0,1,2)、假定原子簇模型V H 鄢x(x=1,2)和V H x'(x=0,1)的电子结构.结果表明:钒与氢气反应生成V H 时,化学效应和结构效应都使V 3d和H 1s轨道向低能量方向移动,氢化物V H 中V 3d和H 1s轨道重叠最多,V -H 之间的相互作用较强。V H 再与氢气反应生成V H 2时,结构效应使V 3d和H 1s轨道都向高能量方向移动,氢化物V H 2中V 3d和H 1s轨道重叠最少,V 和H 之间的相互作用较弱。氢化物V H 和V H 2中不仅存在离子性相互作用,而且还存在共价性相互作用.结构效应导致V H 2中V -H 键的共价性减弱,从而导致V H 2中V 和H 之间的相互作用减弱。氢化物V H 的费米能级比V H 2的低,说明V H 更稳定.展开更多
The effect of equi weight electrostatic field on transesterification of MeCOOBu with EtOH in the presence of base catalyst in liquid phase was investigated. The conversion of forward reaction and backward reaction was...The effect of equi weight electrostatic field on transesterification of MeCOOBu with EtOH in the presence of base catalyst in liquid phase was investigated. The conversion of forward reaction and backward reaction was slightly enhanced in the equi weight field ( E =1×10 5 V/m). SCC DV X α calculations showed that the HOMO energy level of CH 2O was decreased by about 9 6 eV in H + field, while increased by about 23 7 eV in O 2- field. It is concluded that the activation energy of the reaction in equi weight electrostatic field is almost the same as in free field, owing to the same potential energy change of the reactants, transition states and products. In the unequi weight electrostatic field, the negative charge center seems to be the active site for reactants or products, while the positive one seems to be the active site for transition states, resulting in great decrease in the activation energy.展开更多
文摘利用电荷自洽离散变分Xα(SCC-D V-Xα)方法计算了钒基固溶体中钒氢反应前后钒及其氢化物(V H x,x=0,1,2)、假定原子簇模型V H 鄢x(x=1,2)和V H x'(x=0,1)的电子结构.结果表明:钒与氢气反应生成V H 时,化学效应和结构效应都使V 3d和H 1s轨道向低能量方向移动,氢化物V H 中V 3d和H 1s轨道重叠最多,V -H 之间的相互作用较强。V H 再与氢气反应生成V H 2时,结构效应使V 3d和H 1s轨道都向高能量方向移动,氢化物V H 2中V 3d和H 1s轨道重叠最少,V 和H 之间的相互作用较弱。氢化物V H 和V H 2中不仅存在离子性相互作用,而且还存在共价性相互作用.结构效应导致V H 2中V -H 键的共价性减弱,从而导致V H 2中V 和H 之间的相互作用减弱。氢化物V H 的费米能级比V H 2的低,说明V H 更稳定.
文摘The effect of equi weight electrostatic field on transesterification of MeCOOBu with EtOH in the presence of base catalyst in liquid phase was investigated. The conversion of forward reaction and backward reaction was slightly enhanced in the equi weight field ( E =1×10 5 V/m). SCC DV X α calculations showed that the HOMO energy level of CH 2O was decreased by about 9 6 eV in H + field, while increased by about 23 7 eV in O 2- field. It is concluded that the activation energy of the reaction in equi weight electrostatic field is almost the same as in free field, owing to the same potential energy change of the reactants, transition states and products. In the unequi weight electrostatic field, the negative charge center seems to be the active site for reactants or products, while the positive one seems to be the active site for transition states, resulting in great decrease in the activation energy.
