A covalent attraction between two molecular cation TTF·+

The optimized structure of the tetrathiafulvalence radical-cation dimer (TTF·⁺-TTF·⁺) with all-real frequencies is obtained at MP2/6-311G level, which exhibits the attraction between two molecular cation TTF·⁺. The new attraction interaction is a 20-center-2-electron intermolecular covalent π/π bonding with a telescope shape. The covalent π/π bonding has the bonding energy of about ?21 kcal·mol^?1 and is concealed by the Coulombic repulsion between two TTF·⁺ cations. This intermolecular covalent attraction also influences the structure of the TTF·⁺ subunit, i.e., its molecular plane is bent by an angle θ = 5.6°. This work provides new knowledge on intermolecular interaction.

     

两个四硫富瓦烯分子正离子自由基TTF·^＋之间的共价吸引作用

使用MP2／6-311G方法得到了四硫富瓦烯自由基正离子二聚体（TTF·^＋ -TTF·^＋）能量极小点的结构．这显示这种正离子间的吸引作用存在．这种新的吸引作用是望远镜形状的20中心2电子分子间共价π/π键．这种共价π/π键的键能约为-21kcal·mol^-1,它被正离子间的库伦排斥作用掩盖．有负离子围绕的四硫富瓦烯自由基正离子二聚体（TTF·^＋ -TTF·^＋）体系是稳定的．     

Evaluation of dimension of fractal time series with the least square method

<正>Properties of fractional Brownian motions(f Bms)have been investigated by researchers in different fields,e.g.statistics,hydrology,biology,finance,and public transportation,which has helped us better understand many complex time series observed in nature[1-4].The Hurst exponent H(0H1)is the most important parameter characterizing any given time series F(t),where t represents the time steps,and the fractal     

A covalent attraction between two molecular cation TTF·+

The optimized structure of the tetrathiafulvalence radical-cation dimer (TTF·⁺-TTF·⁺) with all-real frequencies is obtained at MP2/6-311G level, which exhibits the attraction between two molecular cation TTF·⁺. The new attraction interaction is a 20-center-2-electron intermolecular covalent π/π bonding with a telescope shape. The covalent π/π bonding has the bonding energy of about −21 kcal·mol⁻¹ and is concealed by the Coulombic repulsion between two TTF·⁺ cations. This intermolecular covalent attraction also influences the structure of the TTF·⁺ subunit, i.e., its molecular plane is bent by an angle θ = 5.6°. This work provides new knowledge on intermolecular interaction.