la1xpbxmno3(x=0～0.5)性質(zhì)的第一性原理研究

1、南京師范大學(xué)碩士學(xué)位論文La1-xPbxMnO3(x=0~0.5)性質(zhì)的第一性原理研究姓名：孫興花申請(qǐng)學(xué)位級(jí)別：碩士專業(yè)：物理；凝聚態(tài)物理指導(dǎo)教師：陳凌孚2009-05-23Abstract - II - Abstract The Density of States of Perovskite La1-xPbxMnO3 (x=0~0.5) with different doping is studied by ab initio ban

2、d caculations based on the Density Functional Theory by a supercell approach. First, using the Local Density Approximation for the exchange-correlation potential , we optimize the undoped ground state of LaMnO3 in the Pe

3、rovskite structure. The picture of Density of States demonstrated that LaMnO3 is an antiferromagnetic insulator.Our calculated energy gap is 0.4eV, which is smaller than experimental value. From the analysis of the Densi

4、ty of States picture of LaMnO3, we find that the valance bands and the conduction bands are composed mainly of O 2p states hybridized with Mn 3d states. The electronic states of La is maily distributed on the conduction

5、bands from 1.5ev to 2.0ev.The result is in good agreement with experimental XPS measurements. Then we calculate the magnetic properties of La1-xPbxMnO3 doped with different quantity. The caculation shows that the system

6、will become ferromagnetic semi-metal when the doping quantity x=0.375.The obitals across the Fermi Level are mainly constituted by the 2p state of O and the 3d state of Mn.The mechanism of the change is : the doping of i

7、mpurity Pb resulted in the mix valence Mn3+ and Mn4+of the Perovskite system .And because the Mn4+ has no eg electron none local like Mn3+,when the doping comes to a level ,the system becomes ferromagnetic because of the