Based on density functional theory and electronegativity equalization principle, a σπ model, which considers the structure of double bond for the first time, is developed. In this model the double bond is partitione...Based on density functional theory and electronegativity equalization principle, a σπ model, which considers the structure of double bond for the first time, is developed. In this model the double bond is partitioned into one σ bond region and four π bond regions. The atom bond electronegativity equalization method plus σπ model(ABEEM σπ ) is then proposed for the calculation of charge distribution and charge polarization in large molecules. It has been shown that the results of charge distribution in large molecules obtained by ABEEM σπ model agree with those obtained by ab initio method very well. In addition, the model can be used to explain the region selectivity of Diels Alder reaction successfully. All these indicate that ABEEM σπ model is reasonable and reliable.展开更多
Two novel topological electro-negativity indices based on distance matrix,named YC and WC indices,were proposed to be used for modeling properties of multiple bond organic compounds by equilibrium electro-negativity o...Two novel topological electro-negativity indices based on distance matrix,named YC and WC indices,were proposed to be used for modeling properties of multiple bond organic compounds by equilibrium electro-negativity of atom and relative bond length of molecule.A quantitative structural property relationship(QSPR) model for estimating flash point of 92 compounds was developed based on the newly introduced topological electro-negativity indices YC and WC and path number parameter P3.The model correlation coefficient and standard error for training set in multiple linear regression were 0.9923 and 5.28,respectively.The average absolute error of flash point was only 3.86 K between experimental and calculated values,and the relative error was 1.46%.Furthermore,the model was strictly tested by both internal and external validations.The predicted values were in good agreement with experimental values for leave-one-out(LOO),and the training set and validation set.The results show that this QSPR model is of good stability and powerful prediction ability.展开更多
对于稀土永磁材料,定义了稀土元素与其他元素之间的加权平均电负性差P和加权平均原子赝势半径差Q;计算了1∶5型RE Co永磁材料、2∶17型RE Co永磁材料、Nd Fe B系列以及双相纳米晶复合材料等具有较好磁性能的稀土永磁材料的P和Q值点;计...对于稀土永磁材料,定义了稀土元素与其他元素之间的加权平均电负性差P和加权平均原子赝势半径差Q;计算了1∶5型RE Co永磁材料、2∶17型RE Co永磁材料、Nd Fe B系列以及双相纳米晶复合材料等具有较好磁性能的稀土永磁材料的P和Q值点;计算结果表明,这些P和Q值点基本上分布在一段特定的区域内。展开更多
文摘Based on density functional theory and electronegativity equalization principle, a σπ model, which considers the structure of double bond for the first time, is developed. In this model the double bond is partitioned into one σ bond region and four π bond regions. The atom bond electronegativity equalization method plus σπ model(ABEEM σπ ) is then proposed for the calculation of charge distribution and charge polarization in large molecules. It has been shown that the results of charge distribution in large molecules obtained by ABEEM σπ model agree with those obtained by ab initio method very well. In addition, the model can be used to explain the region selectivity of Diels Alder reaction successfully. All these indicate that ABEEM σπ model is reasonable and reliable.
文摘Two novel topological electro-negativity indices based on distance matrix,named YC and WC indices,were proposed to be used for modeling properties of multiple bond organic compounds by equilibrium electro-negativity of atom and relative bond length of molecule.A quantitative structural property relationship(QSPR) model for estimating flash point of 92 compounds was developed based on the newly introduced topological electro-negativity indices YC and WC and path number parameter P3.The model correlation coefficient and standard error for training set in multiple linear regression were 0.9923 and 5.28,respectively.The average absolute error of flash point was only 3.86 K between experimental and calculated values,and the relative error was 1.46%.Furthermore,the model was strictly tested by both internal and external validations.The predicted values were in good agreement with experimental values for leave-one-out(LOO),and the training set and validation set.The results show that this QSPR model is of good stability and powerful prediction ability.
文摘对于稀土永磁材料,定义了稀土元素与其他元素之间的加权平均电负性差P和加权平均原子赝势半径差Q;计算了1∶5型RE Co永磁材料、2∶17型RE Co永磁材料、Nd Fe B系列以及双相纳米晶复合材料等具有较好磁性能的稀土永磁材料的P和Q值点;计算结果表明,这些P和Q值点基本上分布在一段特定的区域内。
