含有开壳层4f局域电子的稀土材料体系,因其独特的物理化学性质而在基础和应用研究领域受到广泛关注.从第一性原理理论计算的角度,通常的局域密度近似或广义梯度近似下的密度泛函理论(DFT)方法,因为对局域f-电子的描述存在严重的自相互作用误差,难以正确描述这一类强关联体系的基态性质.被广泛地应用于强关联材料的第一性原理计算的DFT+U方法,通常需要人为指定屏蔽库伦作用参数,削弱了它对新体系的预测能力.本工作中,我们在密度泛函理论的框架下,采用Thomas-Fermi模型,发展了一种体系自洽的局域屏蔽库伦修正方法,该方法基于局域空间内的电子密度自洽地获得体系依赖的屏蔽作用参数.将该方法应用于研究EuX(X=O,S,Se,Te)体系的电子能带结构和磁性质,取得了较为合理的结果,验证了方法的有效性.
Open shell systems with f-electrons are of great importance for their special electronic and magnetic properties.But self-interaction error has serious effects on these systems,and makes it hard to describe by only conventional DFT methods (e.g.LDA and GGA).The DFT + U method,which is widely used in first-principles studies of strongly-correlated systems,depends on the local Coulomb interaction parameters that are often chosen empirically.In this work,a local screened Coulomb correction approach was proposed,in which the on-site Coulomb interaction parameters were determined based on the local electron density in terms of the Thomas-Fermi screening model in a system-dependent and self-consistent way.This approach was applied to investigate electronic and magnetic properties of EuX (X =O,S,Se and Te) with reasonable agreement with experiment.
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