The valence bond structure of substitutional BCC based Ta-W alloys is studied using characteristic crystal （CC） theory. This theory is based on cluster statistics of random alloys. By studying the correlativity betw...The valence bond structure of substitutional BCC based Ta-W alloys is studied using characteristic crystal （CC） theory. This theory is based on cluster statistics of random alloys. By studying the correlativity between energy and volume of the CC in Ta- W alloys, the valence bond structure of CC is determined by the energy and shape method. Then, following additive law of CC, the valence bond structure of Ta-W alloys is calculated. It is found that the outer shell valence electronic distribution of Ta-W Mloys shows a continuous change in the whole composition range. The covalent electrons ec （dc, sc, and pc） increase, whereas near free electrons ef decrease with increasing W concentration. The bond length and single-bond radius decrease, whereas bond energy and bond valence increase with increasing W concentration. The mechanism of solid solution strengthening of Ta-W alloys is analyzed based on their valence bond structure.展开更多
On the basis of energy and shape method for the determination of the valence bond （ VB ） structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole ...On the basis of energy and shape method for the determination of the valence bond （ VB ） structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole temperature range of 0-1943K. The outer shell electronic distribution of Ti is ec^29907. （sc^0.4980 ＋ dc^2.4927） ef^1.0098 in crystal. The temperature dependences of the VB structures of hcp and bcc phases are the same. The VB structures of hcp and bcc phases monotonically increase or decrease with the increase in temperature, but show discontinuous changes at the phase-transformation temperature 1155K.展开更多
Bonded tableau unitary group approach (BTUGA) is applied to the isoelec tronic series XO3 (X=B2-,C-, N and O+) and BF3 in the ab initio level. The relationship between structures and properties is analyzed. Results sh...Bonded tableau unitary group approach (BTUGA) is applied to the isoelec tronic series XO3 (X=B2-,C-, N and O+) and BF3 in the ab initio level. The relationship between structures and properties is analyzed. Results show that classical valence bond theory presented unsatisfactory descriptions on these systems and the diradical structures hold an important position in the groud state wavefunctions of the above systems. The structural weight of the diradical resonance structure in a system obviously correlates with the oxidizing power of the system.展开更多
Based on the symmetry of the valence bond wavefunction and the correspondence between bonding patterns and bonded tableaus for chemical bonds in the ground and excited states, the conservation of orbital symmetry and ...Based on the symmetry of the valence bond wavefunction and the correspondence between bonding patterns and bonded tableaus for chemical bonds in the ground and excited states, the conservation of orbital symmetry and the bond symmetry rule can be expressed as "symmetry-adaptation of the valence bond (VB) structure". The symmetry-adaptation of the valence bond structure can directly predict the chemical reactivity by a symmetry analysis of the VB structures of reactants and products without carrying out explicitly theoretical calculations. Curve-crossing diagrams for atom exchange reactions H+HLi→H-2+Li and H+LiH→HLiH (cyclic)→HLi+H have been constructed with the multistructure VB approach and the valence bond structure symmetry rule. The formation mechanism of the barrier and the transition state was discussed. The calculated results show that the H exchange reaction H+LiH HLi+H is a two-step reaction.展开更多
基金supported by Xiangtan University Doctor Research Foundation(GrantNo.08QDZ32)
文摘The valence bond structure of substitutional BCC based Ta-W alloys is studied using characteristic crystal （CC） theory. This theory is based on cluster statistics of random alloys. By studying the correlativity between energy and volume of the CC in Ta- W alloys, the valence bond structure of CC is determined by the energy and shape method. Then, following additive law of CC, the valence bond structure of Ta-W alloys is calculated. It is found that the outer shell valence electronic distribution of Ta-W Mloys shows a continuous change in the whole composition range. The covalent electrons ec （dc, sc, and pc） increase, whereas near free electrons ef decrease with increasing W concentration. The bond length and single-bond radius decrease, whereas bond energy and bond valence increase with increasing W concentration. The mechanism of solid solution strengthening of Ta-W alloys is analyzed based on their valence bond structure.
基金supported by the National Natural Science Foundation of China(No.50271085).
文摘On the basis of energy and shape method for the determination of the valence bond （ VB ） structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole temperature range of 0-1943K. The outer shell electronic distribution of Ti is ec^29907. （sc^0.4980 ＋ dc^2.4927） ef^1.0098 in crystal. The temperature dependences of the VB structures of hcp and bcc phases are the same. The VB structures of hcp and bcc phases monotonically increase or decrease with the increase in temperature, but show discontinuous changes at the phase-transformation temperature 1155K.
文摘Bonded tableau unitary group approach (BTUGA) is applied to the isoelec tronic series XO3 (X=B2-,C-, N and O+) and BF3 in the ab initio level. The relationship between structures and properties is analyzed. Results show that classical valence bond theory presented unsatisfactory descriptions on these systems and the diradical structures hold an important position in the groud state wavefunctions of the above systems. The structural weight of the diradical resonance structure in a system obviously correlates with the oxidizing power of the system.
文摘Based on the symmetry of the valence bond wavefunction and the correspondence between bonding patterns and bonded tableaus for chemical bonds in the ground and excited states, the conservation of orbital symmetry and the bond symmetry rule can be expressed as "symmetry-adaptation of the valence bond (VB) structure". The symmetry-adaptation of the valence bond structure can directly predict the chemical reactivity by a symmetry analysis of the VB structures of reactants and products without carrying out explicitly theoretical calculations. Curve-crossing diagrams for atom exchange reactions H+HLi→H-2+Li and H+LiH→HLiH (cyclic)→HLi+H have been constructed with the multistructure VB approach and the valence bond structure symmetry rule. The formation mechanism of the barrier and the transition state was discussed. The calculated results show that the H exchange reaction H+LiH HLi+H is a two-step reaction.
