铬和镁掺杂对尖晶石LiMn2O4中Jahn-Teller畸变的抑制：GGA和GGA +U的第一性原理研究
Suppression of Jahn-Teller distortion by chromium and magnesium doping in spinel LiMn2O4: A first-principles study using GGA and GGA+U
摘要：
采用第一性原理自旋密度泛函理论，在GGA（广义梯度近似）和GGA+U下研究了铬和镁掺杂对尖晶石LiMn 2 O 4的影响.我们发现GGA和GGA+U对LiMn_2 O_4的基态不同，而对掺杂体系的基态相同。对于LiMn_2O_4，GGA和GGA+U的基态结构为体心四方相，而对于LiM_0.5Mn_1.5O_4（M= Cr或Mg）的基态结构为基心单斜相，对于LiMM_nO_4（M= Cr或Mg）的基态结构和GGA+U的基态结构均为体心正交相。我们发现，GGA预测的原始LiMn_2O_4是金属，而GGA+U预测它是绝缘的，这是符合实验观察。对于掺杂尖晶石，GGA预测基态是半金属的，而GGA+U预测它是绝缘的或金属的，这取决于掺杂浓度。GGA+U预测绝缘体-金属-绝缘体转变作为掺杂的函数的情况下的Cr和Mg的情况下的基态被发现从绝缘到半金属状态作为掺杂的函数。电荷密度和态密度的分析表明，电荷从掺杂剂转移到相邻的氧原子和锰原子。我们用GGA和GGA+U计算了掺杂化合物的Jahn-Teller激活模位移Q_3。由GGA+U计算的键长与实验值吻合较好。基于金属和氧的键长，我们还估计了掺杂剂的平均氧化态。
英文摘要：
The effect of doping spinel LiMn2O4 with chromium and magnesium has been studied using the first-principles spin density functional theory within GGA (generalized gradient approximation) and GGA+U. We find that GGA and GGA+U give different ground states for pristine LiMn2O4 and same ground state for doped systems. For LiMn2O4 the body centered tetragonal phase was found to be the ground state structure using GGA and face centered orthorhombic using GGA+U, while for LiM0.5Mn1.5O4 (M= Cr or Mg) it was base centered monoclinic and for LiMMnO4 (M= Cr or Mg) it was body centered orthorhombic in both GGA and GGA+U. We find that GGA predicts the pristine LiMn2O4 to be metallic while GGA+U predicts it to be the insulating which is in accordance with the experimental observations. For doped spinels, GGA predicts the ground state to be half metallic while GGA+U predicts it to be insulating or metallic depending on the doping concentration. GGA+U predicts insulator-metal-insulator transition as a function of doping in case of Cr and in case of Mg the ground state is found to go from insulating to a half metallic state as a function of doping. Analysis of the charge density and the density of states suggest a charge transfer from the dopants to the neighboring oxygen atoms and manganese atoms. We have calculated the Jahn-Teller active mode displacement Q3 for doped compounds using GGA and GGA+U. The bond lengths calculated from GGA+U are found to be in better agreement with the experimental bond lengths. Based on the bond lengths of metal and oxygen, we have also estimated the average oxidation states of the dopants.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
