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本文用能量梯度法TEXAS从头计算程序,选取4-21G及4-21G~*(O,N原子含极化d轨道)基组,对α-,β-,γ-吡啶甲酸分子的平衡几何构型进行了全优化计算.二套基组的理论优化表明,三个吡啶甲酸分子都具有平面的平衡构型.其计算键长经4-21G基组的标准经验校正值校正后,所得的理论预测平衡几何构型与X射线单晶衍射实验结果有很好的一致性.对部分键长以及羧基与吡啶环平面的二面角中出现的差异进行了讨论.
In this paper, we use the energy gradient method TEXAS ab initio calculation program to select the equilibrium geometry of α-, β-, γ-picolinic acid from 4-21G and 4-21G ~ * (O, N atoms with polar d orbitals) basis set Type.The theoretical optimization of the two sets of basic groups shows that all the three picolinic acid molecules have a planar equilibrium configuration.After calculating the bond length by the standard empirical correction value of 4-21G basis set, The predicted equilibrium geometry is in good agreement with the X-ray single crystal diffraction results, and some differences in the partial bond length and the dihedral angle between the carboxyl group and the pyridine ring plane are discussed.