α-Pu和δ-Pu电子结构的密度泛函理论计算
|
摘要
采用密度泛函理论框架下的平面波赝势方法,对α-Pu和δ-Pu的电子结构进行了对比研究。由电荷布居分析可知,α-Pu中8种位置的原子的轨道电荷分布各不相同,净电荷的得失主要由s和p电子贡献,而δ-Pu中各原子的轨道电荷分布一致,且无净电荷的得失;由态密度可知,α-Pu的态密度主峰较δ-Pu的态密度主峰峰值更低、宽度更宽,表明α-Pu中平均键能强于δ-Pu,导致其更难发生塑性形变。此外,α-Pu电子的能量总体上低于δ-Pu电子的,这也是α-Pu的室温稳定性高于δ-Pu的重要原因。α-Pu中8种不同位置Pu原子的分波态密度的计算结果表明,8号位置Pu原子的5f电子关联性最强,对α-Pu的自旋矩贡献最大,而1号位置Pu原子的5f电子关联性最弱,对自旋矩的贡献最小;由电荷密度图可知,δ-Pu的电子云为均匀的球形,无明显的相互作用,呈现典型的金属键特征,而α-Pu的电子云发生重叠,相互作用明显,具有共价行为,这也在一定程度上揭示了两者呈现不同延脆性机制。
The comparative study between the electronic structures of α-Pu and δ-Pu was conducted by aplane wave pseudo-potential method within the framework of density functional theory.It's learned from the charge population that the 8kinds of atoms in α-Pu have different charge distributions,and the gain and loss of net charge are mainly contributed by s and pelectrons,while the atoms in δ-Pu have the same charge distribution with no gain or loss of net charge.It's learned from density of states(DOS)that α-Pu has relatively lower and wilder DOS peak than δ-Pu,indicating that the average bond energy of α-Pu is stronger than that of δ-Pu,which results in a more difficult plas-tic deformation for α-Pu.Besides,the energy of α-Pu electrons is generally lower than that of δ-Pu electrons,which is an important reason for the better stability of α-Pu at room temperature.And it's learned from partial density of states(PDOS)that,the correlation of 5felectrons of Pu atom at site 8is the strongest,with the greatest contribution to the spin moment of α-Pu,while at site 1it is the weakest,with the smallest contribution to the spin moment.It's learned from the electron density that the atoms in δ-Pu have round electron clouds without obvious interaction,presenting the typical feature of metallic bonds,while the electron clouds of atoms in α-Pu overlap with each other and the bonds are covalent in character,which to some degree reveals the mechanism of different ductility and brittleness of δ-Pu and α-Pu.
The comparative study between the electronic structures of α-Pu and δ-Pu was conducted by aplane wave pseudo-potential method within the framework of density functional theory.It's learned from the charge population that the 8kinds of atoms in α-Pu have different charge distributions,and the gain and loss of net charge are mainly contributed by s and pelectrons,while the atoms in δ-Pu have the same charge distribution with no gain or loss of net charge.It's learned from density of states(DOS)that α-Pu has relatively lower and wilder DOS peak than δ-Pu,indicating that the average bond energy of α-Pu is stronger than that of δ-Pu,which results in a more difficult plas-tic deformation for α-Pu.Besides,the energy of α-Pu electrons is generally lower than that of δ-Pu electrons,which is an important reason for the better stability of α-Pu at room temperature.And it's learned from partial density of states(PDOS)that,the correlation of 5felectrons of Pu atom at site 8is the strongest,with the greatest contribution to the spin moment of α-Pu,while at site 1it is the weakest,with the smallest contribution to the spin moment.It's learned from the electron density that the atoms in δ-Pu have round electron clouds without obvious interaction,presenting the typical feature of metallic bonds,while the electron clouds of atoms in α-Pu overlap with each other and the bonds are covalent in character,which to some degree reveals the mechanism of different ductility and brittleness of δ-Pu and α-Pu.
引文
[1]李如松,何彬,许鹏,等.Pu化合物电子结构的密度泛函理论计算[J].原子能科学技术,2014,48(增刊):43-49.LI Rusong,HE Bin,XU Peng,et al.Density function theory calculation for electronic structures of plutonium compounds[J].Atomic Energy Science and Technology,2014,48(Suppl.):43-49(in Chinese).
[2]李冠兴,武胜.核燃料[M].北京:化学工业出版社,2007.
[3]王同权,于万瑞,冯煜芳.钚材料的老化[J].原子核物理评论,2006,23(3):343-347.WANG Tongquan,YU Wanrui,FENG Yufang.Overview of plutonium aging[J].Nuclear Physics Review,2006,23(3):343-347(in Chinese).
[4]敖冰云,叶小球,陈丕恒.钚固体材料理论研究进展[J].物理化学学报,2015,31(增刊):3-13.AO Bingyun,YE Xiaoqiu,CHEN Piheng.Progress in theoretical research on plutonium-based solid-state materials[J].Acta Physico-Chimica Sinica,2015,31(Suppl.):3-13(in Chinese).
[5]伍冬兰,谭彬,温玉峰,等.MgH分子特性和势能随外场的变化规律[J].原子能科学技术,2015,49(12):2 118-2 123.WU Donglan,TAN Bin,WEN Yufeng,et al.Change law of MgH molecular characteristics and potential energy with external electric field[J].Atomic Energy Science and Technology,2015,49(12):2 118-2 123(in Chinese).
[6]YE L H,LUO N,PENG L M.Dielectric constant of NiO and LDA+U[J].Physical Review B,2013,87(7):075115-075121.
[7]马贺,陈立佳,郭连权,等.金属Al电子结构与热力学性质的第一性原理计算[J].沈阳工业大学学报,2015,37(4):399-403.MA He,CHEN Lijia,GUO Lianquan,et al.First-principle calculation for electronic structure and thermodynamic properties of metal Al[J].Journal of Shenyang University of Technology,2015,37(4):399-403(in Chinese).
[8]SCLAUZERO G,EDERER C.Structural and electronic properties of epitaxially strained LaVO3 from density functional theory and dynamical mean-field theory[J].Physical Review B,2015,92(23):583-586.
[9]SADIGH B,WOLFER W G.Gallium stabilization ofδ-Pu:Density-function calculations[J].Physical Review B,2005,72(20):2 424-2 433.
[10]SDERLIND P,KLEPEIS J E.First-principles elastic properties ofα-Pu[J].Physical Review B,2009,79(10):104110.
[11]SUN B,ZHANG P.First-principles local density approximation(LDA)+U and generalized approximation(GGA)+U studies of plutonium oxides[J].Chinese Physics B,2008,17(4):1 364-1 370.
[12]李赣,赖新春,孙颖.FLAPW方法研究δ-钚单层表面几何和电子结构[J].物理化学学报,2005,21(6):686-689.LI Gan,LAI Xinchun,SUN Ying.An all-electron FLAPW study of geometric and electronic structures forδ-pumonolayer[J].Acta PhysicoChimica Sinica,2005,21(6):686-689(in Chinese).
[13]ZHU J X,MCMAHAN A K,JONES M D,et al.Spectral properties ofδ-plutonium:Sensitivity to 5f occupancy[J].Physical Review B,2007,76(24):245 118-245 123.
[14]DAI Xi.Topological phases in mix valence rareearth compounds[C]∥首届中国锕系物理化学学术交流会论文摘要集.绵阳:中国工程物理研究院,2014.
[15]李如松,何彬,李刚,等.基于密度泛函理论方法的δ相Pu 5f状态电子结构计算[J].物理化学学报,2015,31(增刊):75-80.LI Rusong,HE Bin,LI Gang,et al.An electronic structure calculation for 5f states ofδphase plutonium based on the density functional theory method[J].Acta Physico-Chimica Sinica,2015,31(Suppl.):75-80(in Chinese).
[16]WICK O J.Plutonium handbook:A guide to the technology[M].US:Gordon and Breach Science Publishers Inc.,1967.
[17]刘以良,肖培.δ-Pu态密度的动力学平均场理论研究[J].西南民族大学学报:自然科学版,2010,36(6):1 014-1 017.LIU Yiliang,XIAO Pei.Density of state study forδ-Pu with dynamical mean-field theory[J].Journal of Southwest University for Nationalities:Natural Science Edition,2010,36(6):1 014-1 017(in Chinese).
[18]杨晓敏.Mg-Al基强化相及固溶体结构和性能的第一性原理研究[D].太原:中北大学,2014.
[19]庄严,陈敬超,吕连灏.第一性原理研究铱金属的致脆机理[J].材料导报B:研究篇,2015,29(1):150-154.ZHUANG Yan,CHEN Jingchao,LV Lianhao.First-principles study on the embrittlement mechanism of iridium metal[J].Materials Review B,2015,29(1):150-154(in Chinese).
[2]李冠兴,武胜.核燃料[M].北京:化学工业出版社,2007.
[3]王同权,于万瑞,冯煜芳.钚材料的老化[J].原子核物理评论,2006,23(3):343-347.WANG Tongquan,YU Wanrui,FENG Yufang.Overview of plutonium aging[J].Nuclear Physics Review,2006,23(3):343-347(in Chinese).
[4]敖冰云,叶小球,陈丕恒.钚固体材料理论研究进展[J].物理化学学报,2015,31(增刊):3-13.AO Bingyun,YE Xiaoqiu,CHEN Piheng.Progress in theoretical research on plutonium-based solid-state materials[J].Acta Physico-Chimica Sinica,2015,31(Suppl.):3-13(in Chinese).
[5]伍冬兰,谭彬,温玉峰,等.MgH分子特性和势能随外场的变化规律[J].原子能科学技术,2015,49(12):2 118-2 123.WU Donglan,TAN Bin,WEN Yufeng,et al.Change law of MgH molecular characteristics and potential energy with external electric field[J].Atomic Energy Science and Technology,2015,49(12):2 118-2 123(in Chinese).
[6]YE L H,LUO N,PENG L M.Dielectric constant of NiO and LDA+U[J].Physical Review B,2013,87(7):075115-075121.
[7]马贺,陈立佳,郭连权,等.金属Al电子结构与热力学性质的第一性原理计算[J].沈阳工业大学学报,2015,37(4):399-403.MA He,CHEN Lijia,GUO Lianquan,et al.First-principle calculation for electronic structure and thermodynamic properties of metal Al[J].Journal of Shenyang University of Technology,2015,37(4):399-403(in Chinese).
[8]SCLAUZERO G,EDERER C.Structural and electronic properties of epitaxially strained LaVO3 from density functional theory and dynamical mean-field theory[J].Physical Review B,2015,92(23):583-586.
[9]SADIGH B,WOLFER W G.Gallium stabilization ofδ-Pu:Density-function calculations[J].Physical Review B,2005,72(20):2 424-2 433.
[10]SDERLIND P,KLEPEIS J E.First-principles elastic properties ofα-Pu[J].Physical Review B,2009,79(10):104110.
[11]SUN B,ZHANG P.First-principles local density approximation(LDA)+U and generalized approximation(GGA)+U studies of plutonium oxides[J].Chinese Physics B,2008,17(4):1 364-1 370.
[12]李赣,赖新春,孙颖.FLAPW方法研究δ-钚单层表面几何和电子结构[J].物理化学学报,2005,21(6):686-689.LI Gan,LAI Xinchun,SUN Ying.An all-electron FLAPW study of geometric and electronic structures forδ-pumonolayer[J].Acta PhysicoChimica Sinica,2005,21(6):686-689(in Chinese).
[13]ZHU J X,MCMAHAN A K,JONES M D,et al.Spectral properties ofδ-plutonium:Sensitivity to 5f occupancy[J].Physical Review B,2007,76(24):245 118-245 123.
[14]DAI Xi.Topological phases in mix valence rareearth compounds[C]∥首届中国锕系物理化学学术交流会论文摘要集.绵阳:中国工程物理研究院,2014.
[15]李如松,何彬,李刚,等.基于密度泛函理论方法的δ相Pu 5f状态电子结构计算[J].物理化学学报,2015,31(增刊):75-80.LI Rusong,HE Bin,LI Gang,et al.An electronic structure calculation for 5f states ofδphase plutonium based on the density functional theory method[J].Acta Physico-Chimica Sinica,2015,31(Suppl.):75-80(in Chinese).
[16]WICK O J.Plutonium handbook:A guide to the technology[M].US:Gordon and Breach Science Publishers Inc.,1967.
[17]刘以良,肖培.δ-Pu态密度的动力学平均场理论研究[J].西南民族大学学报:自然科学版,2010,36(6):1 014-1 017.LIU Yiliang,XIAO Pei.Density of state study forδ-Pu with dynamical mean-field theory[J].Journal of Southwest University for Nationalities:Natural Science Edition,2010,36(6):1 014-1 017(in Chinese).
[18]杨晓敏.Mg-Al基强化相及固溶体结构和性能的第一性原理研究[D].太原:中北大学,2014.
[19]庄严,陈敬超,吕连灏.第一性原理研究铱金属的致脆机理[J].材料导报B:研究篇,2015,29(1):150-154.ZHUANG Yan,CHEN Jingchao,LV Lianhao.First-principles study on the embrittlement mechanism of iridium metal[J].Materials Review B,2015,29(1):150-154(in Chinese).