论文标题

有效的优化方法,用于寻找磁性转换的最小能量路径

Efficient Optimization Method for Finding Minimum Energy Paths of Magnetic Transitions

论文作者

Ivanov, Aleksei V., Dagbartsson, Damjan, Tranchida, Julien, Uzdin, Valery M., Jónsson, Hannes

论文摘要

计算磁过渡的最小能量路径的有效算法是在测量轻度弹性带(GNEB)方法中实现的。虽然无法进行gneb的客观功能,因此不能进行传统的线路搜索,但使用有限的记忆力broyden-fletcher-fletcher-goldfarb-shanno(lbfgs)和共轭梯度算法与正交旋转优化(OSO)的方法相结合,以前显示了以前使用的verifters distriptions distriptions distriptions的反应率,并且 方法。该实现利用能量加权弹簧将离散点沿着路径的分布进行分配,发现这可以显着提高性能。各种方法都应用于使用海森堡型哈密顿量的几个测试问题,在某些情况下扩展为包括dzyaloshinskii-Moriya,以及最近邻居以外的交换相互作用。在纳米岛中发现了最小能量路径,可用于磁化逆转,二维层中的天空塌陷以及三维磁铁表面附近的手性浮球的歼灭。在某些情况下,发现LBFGS-OSO方法比基于动态的方法的表现高达8倍。

Efficient algorithms for the calculation of minimum energy paths of magnetic transitions are implemented within the geodesic nudged elastic band (GNEB) approach. While an objective function is not available for GNEB and a traditional line search can, therefore, not be performed, the use of limited memory Broyden-Fletcher-Goldfarb-Shanno (LBFGS) and conjugate gradient algorithms in conjunction with orthogonal spin optimization (OSO) approach is shown to greatly outperform the previously used velocity projection and dissipative Landau-Lifschitz dynamics optimization methods. The implementation makes use of energy weighted springs for the distribution of the discretization points along the path and this is found to improve performance significantly. The various methods are applied to several test problems using a Heisenberg-type Hamiltonian, extended in some cases to include Dzyaloshinskii-Moriya and exchange interactions beyond nearest neighbours. Minimum energy paths are found for magnetization reversals in a nano-island, collapse of skyrmions in two-dimensional layers and annihilation of a chiral bobber near the surface of a three-dimensional magnet. The LBFGS-OSO method is found to outperform the dynamics based approaches by up to a factor of 8 in some cases.

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