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arXiv 1409.8312cond-mat.str-el
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过渡金属一氧化物准粒子自洽GW计算的收敛性

Convergence of quasiparticle self-consistent GW calculations of transition metal monoxides

Suvadip Das, John E. Coulter, Efstratios Manousakis

摘要:

寻找一个精确的从头计算方法来计算过渡金属氧化物的电子性质已经是一个问题了几十年。在本文中,我们研究了过渡金属一氧化物MnO,CoO和NiO的电子结构在其未扭曲的岩盐结构内的完全迭代准粒子自洽GW(QPscGW)计划。我们研究了QPscGW方法的收敛性,即,准粒子能量本征值和波函数如何收敛作为QPscGW迭代的函数,并且我们比较了从不同起始波函数获得的收敛输出。我们发现,收敛是缓慢的,一个一次性的G $_0$ W $_0$计算并没有显着提高初始特征值和状态。重要的是要注意,在某些情况下,收敛的“路径”可能会经过能带重排,这不能被简单的初始未扰动哈密顿量所捕获。当我们达到一个完全迭代的解决方案,收敛的态密度,带隙和磁矩的这些氧化物被发现是只有弱依赖于选择的起始波函数,并在合理的良好协议与实验。最后,这种方法提供了一个清晰的图片附近的费米能级的这些简单的过渡金属一氧化物的各种轨道之间的相互作用。这些精确的{ \it ab initio}计算的结果可以为旨在描述这些材料中的低能物理的模型提供输入。

英文摘要:

Finding an accurate ab initio approach for calculating the electronic properties of transition metal oxides has been a problem for several decades. In this paper, we investigate the electronic structure of the transition metal monoxides MnO, CoO, and NiO in their undistorted rock-salt structure within a fully iterated quasiparticle self-consistent GW (QPscGW) scheme. We study the convergence of the QPscGW method, i.e., how the quasiparticle energy eigenvalues and wavefunctions converge as a function of the QPscGW iterations, and we compare the converged outputs obtained from different starting wavefunctions. We find that the convergence is slow and that a one-shot G$_0$W$_0$ calculation does not significantly improve the initial eigenvalues and states. It is important to notice that in some cases the "path" to convergence may go through energy band reordering which cannot be captured by the simple initial unperturbed Hamiltonian. When we reach a fully iterated solution, the converged density of states, band-gaps and magnetic moments of these oxides are found to be only weakly dependent on the choice of the starting wavefunctions and in reasonably good agreement with the experiment. Finally, this approach provides a clear picture of the interplay between the various orbitals near the Fermi level of these simple transition metal monoxides. The results of these accurate {\it ab initio} calculations can provide input for models aiming at describing the low energy physics in these materials.

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