Benali Anouar, Shulenburger Luke, Krogel Jaron T, Zhong Xiaoliang, Kent Paul R C, Heinonen Olle
Argonne Leadership Computing Facility, Argonne National Laboratory, Argonne, Illinois 60439, USA.
Phys Chem Chem Phys. 2016 Jul 21;18(27):18323-35. doi: 10.1039/c6cp02067d. Epub 2016 Jun 23.
The Magnéli phase Ti4O7 is an important transition metal oxide with a wide range of applications because of its interplay between charge, spin, and lattice degrees of freedom. At low temperatures, it has non-trivial magnetic states very close in energy, driven by electronic exchange and correlation interactions. We have examined three low-lying states, one ferromagnetic and two antiferromagnetic, and calculated their energies as well as Ti spin moment distributions using highly accurate quantum Monte Carlo methods. We compare our results to those obtained from density functional theory-based methods that include approximate corrections for exchange and correlation. Our results confirm the nature of the states and their ordering in energy, as compared with density-functional theory methods. However, the energy differences and spin distributions differ. A detailed analysis suggests that non-local exchange-correlation functionals, in addition to other approximations such as LDA+U to account for correlations, are needed to simultaneously obtain better estimates for spin moments, distributions, energy differences and energy gaps.
马格内利相Ti4O7是一种重要的过渡金属氧化物，由于其电荷、自旋和晶格自由度之间的相互作用，具有广泛的应用。在低温下，受电子交换和关联相互作用驱动，它具有能量非常接近的非平凡磁态。我们研究了三个低能态，一个铁磁态和两个反铁磁态，并使用高精度量子蒙特卡罗方法计算了它们的能量以及Ti自旋矩分布。我们将我们的结果与基于密度泛函理论的方法所得到的结果进行比较，这些方法包括对交换和关联的近似修正。与密度泛函理论方法相比，我们的结果证实了这些态的性质及其能量排序。然而，能量差和自旋分布有所不同。详细分析表明，除了其他近似方法（如用于考虑关联的LDA+U）之外，还需要非局域交换关联泛函，以同时获得对自旋矩、分布、能量差和能隙的更好估计。
