对含重元素体系的接合二分量-标量相对论密度泛函计算方法

在相对论密度泛函ZORA方法的基础上,提出一种用于含重元素体系的接合二分量-标量相对论密度泛函计算方法.对于只含少数几个重元素的较大体系,仅对其中旋轨耦合作用强的重元素作二分量相对论计算,而对体系的其余部分则作标量相对论计算,通过对动能矩阵元的近似处理实现两种计算的接合.对一系列含6p区重元素分子进行计算的结果表明,当非重元素是第三周期以前的元素时,此方法与二分量ZO-RA方法的计算结果吻合得很好.当非重元素为第四周期元素时,计算结果有一定偏差,表明在后一种情况下旋轨耦合作用已比较显著,但误差仍在目前近似密度泛函计算的精度范围内.此方法可以有效地节省计算量,而且避免了Dyall方法的缺点.

A Scheme for Jointed Two Component-scalar Relativistic Density Functional Calculations of Systems Containing Heavy Elements

A scheme for joined two component-scalar relativistic density functional calculations of systems containing a few heavy atoms is proposed based on the relativistic density functional ZORA method with an atomic model potential approximation. The two component-relativistic density functional computation is performed only for a few heavy atoms with strong spin-orbit effects in the system, while the reminder part of the system is treated with the scalar relativistic density functional method, resulting in considerably reduction of computational efforts. The two kinds of computations are joined through a reasonable approximation in the calculation of kinetic energy matrix elements. The calculations for a series of molecules containing 6p block heavy elements are performed by using the proposed scheme and the normal two component-ZORA method. It is found that the results from the two kinds of calculations are in excellent agreement to each other when the lighter atoms belong to the second or third period. If the “non-heavy” atoms belong to the fourth period, the results from the proposed scheme slightly deviate from those obtained by the normal two component-ZORA calculations, showing that the spin-orbit effects have become significant relatively and cannot be neglected in the calculations with a high accuracy required. However, even in that case, the accuracy of the calculated results is still compatible with that of the current approximate density functionals and can satisfied the requirement for ordinary theoretical studies. The proposed scheme can effectively save computation efforts while the defects in Dyall′s method can be avoided.