Typical density-functional theory calculations that wrongly predict undoped cuprates to be metallic also predict Cu-O half- and full-breathing phonon energies that are significantly softer than observed, presumably because of weak on-site Coulomb repulsion on the Cu 3d orbitals. We used $\mathrm{DFT}+\mathrm{U}$ calculations with antiferromagnetic supercells of ${\mathrm{La}}_{\text{2}}{\mathrm{CuO}}_{\text{4}}$ to establish correlation between the on-site repulsion strength, tuned via adjusting the value of U, and phonon dispersions. We find that breathing and half-breathing phonons reach experimental values when U is tuned to obtain the correct optical gap and magnetic moments. We demonstrate that using distorted supercells within $\mathrm{DFT}+\mathrm{U}$ is a promising framework to model phonons in undoped cuprates and other perovskite oxides with complex, interrelated structural and electronic degrees of freedom.

中文翻译：

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使用LDA+U计算的未掺杂La2CuO4中电子电荷间隙对LO键拉伸声子的影响

典型的密度泛函理论计算错误地预测未掺杂的铜酸盐是金属的，也预测 Cu-O 半呼吸和全呼吸声子能量比观察到的要软得多，这可能是因为 Cu 3d轨道上的现场库仑排斥力较弱。我们用了$\mathrm{离散傅立叶变换}+\mathrm{你}$ 用反铁磁超胞计算 ${拉}_{\text{2}}{\mathrm{氧化铜}}_{\text{4}}$建立现场排斥强度（通过调整 U 值进行调整）与声子色散之间的相关性。我们发现当 U 被调谐以获得正确的光学间隙和磁矩时，呼吸和半呼吸声子达到实验值。我们证明了在内部使用扭曲的超级细胞$\mathrm{离散傅立叶变换}+\mathrm{你}$ 是一个很有前景的框架，可以模拟未掺杂的铜酸盐和其他钙钛矿氧化物中具有复杂、相互关联的结构和电子自由度的声子。