论文标题
完整配置互动量子蒙特卡洛中的自适应移位方法：开发和应用
The Adaptive Shift Method in Full Configuration Interaction Quantum Monte Carlo: Development and Applications
论文作者
论文摘要
在最近的一篇论文中，我们提出了一种自适应移位方法，用于纠正引发剂FCIQMC的不足采样偏差。该方法允许步行者数量达到FCI极限的速度比普通启动器方法，尤其是对于大型系统。然而，在应用于强相关的分子中，该方法容易在中间助行器数量上超过FCI能量，并从下面收敛到FCI极限。在本文中，我们提出了一种解决强度分子中过冲问题的解决方案，并进一步加速了与FCI能量的收敛性。这是通过将参考能取消到通常低于Hartree-fock能量但高于确切能量的值来实现的。此抵消过程不会改变算法的精确性属性，即在大巡回赛限制中融合到精确的FCI解决方案，但以其最佳值以极大的加速会加速收敛。此抵消过程没有与此相关的高架成本，因此是纯粹而实质性的计算增益。我们通过将其应用于n $ _2 $分子，三种不同的几何形状（平衡开放式最小值，一个假设的环和过渡状态）中的臭氧分子（在三个基准组中）（cc-pv $ x $ x $ x $ x $ = d，t，q）conccccccccccccccccccccccccccccccccccccccccccccccccccccccccc的28个几何最小，否则cormiim dim cccccc，我们将说明了这种偏移自适应转移方法的行为。 76个轨道。我们表明，在大多数情况下，偏移自适应移位方法的收敛速度要比普通启动器方法和原始自适应移位方法快得多。
In a recent paper, we proposed the adaptive shift method for correcting the undersampling bias of the initiator-FCIQMC. The method allows faster convergence with the number of walkers to the FCI limit than the normal initiator method, particularly for large systems. In its application to strongly correlated molecules, however, the method is prone to overshooting the FCI energy at intermediate walker numbers, with convergence to the FCI limit from below. In this paper, we present a solution to the overshooting problem in strongly correlated molecules, as well as further accelerating convergence to the FCI energy. This is achieved by offsetting the reference energy to a value typically below the Hartree-Fock energy but above the exact energy. This offsetting procedure does not change the exactness property of the algorithm, namely convergence to the exact FCI solution in the large-walker limit, but at its optimal value greatly accelerates convergence. There is no overhead cost associated with this offsetting procedure, and is therefore a pure and substantial computational gain. We illustrate the behavior of this offset adaptive shift method by applying it to the N$_2$ molecule, the ozone molecule at three different geometries (equilibrium open minimum, a hypothetical ring minimum, and a transition state) in three basis sets (cc-pV$X$Z, $X$=D,T,Q), and the chromium dimer in cc-pVDZ basis set, correlating 28 electrons in 76 orbitals. We show that in most cases the offset adaptive shift method converges much faster than both the normal initiator method and the original adaptive shift method.
