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采用基于密度泛函理论的第一性原理方法比较研究了Na1/2Bi1/2TiO3和K1/2Bi1/2TiO3的电子结构、离子位移势能面和Γ声子等性质. 结果表明，Na1/2Bi1/2TiO3和K1/2Bi1/2TiO3的电子结构很相似，价带由O 2p 电子态主导并包含部分 Ti 3d 和 Bi 6p电子态，导带低能部分由Ti 3d空轨道构成; K取代Na后其Ti–O和Bi–O键的键强略有增加. 两者的离子位移势能面也很接近，O离子的偏心位移对结构不稳定性起主导作用，且K取代Na后其作用增强. Γ声子都存在3个软模，分析表明软模主要来自O6基团的振动，K取代Na后A2u软模发生硬化.The electronic structures, potential energy surfaces for the displacement of ions along the tetragonal [001] and Γ phonon properties of Na1/2Bi1/2TiO3 and K1/2Bi1/2TiO3 are investigated by employing the first-principles method based on density functional theory. The results indicate that the electronic structures of Na1/2Bi1/2TiO3 and K1/2Bi1/2TiO3 are very similar. The valence band is dominated by O 2p states with an admixture of Ti 3d and Bi 6p states. The lower energy region of the conduction band is mainly composed of Ti 3d orbitals. The bond strengths of Ti–O and Bi–O increase when Na is substituted by K. Moreover, minor differences are observed from the potential energy surface for the displacement of ions along the tetragonal [001], which indicates that the phase instabilities of the two compounds mainly come from the displacement of O ions, which plays a more important role when Na is substituted by K. There are three soft modes for Na1/2Bi1/2TiO3 and K1/2Bi1/2TiO3, which mainly originate from the vibration of O6 group. The A2u soft mode becomes harder when Na is substituted by K.
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Keywords:
- electronic structure /
- potential energy surface for the displacement of ions /
- Γ phonon /
- first-principles
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[21] Chen W, Li Y, Xu Q, Zhou J 2005 J. Electroceram. 15 229
[22] Sun R, Lin D I, Zhang Q, Fang B, Zhang H, Li X, Wang S, Wang D, Zhao X, Luo H 2011 J. Adv. Dielect. 1 237
[23] Ming B Q, Wang J F, Zang G Z 2008 Chin. Phys. Lett. 25 3776
[24] Milman V, Winkler B, White J A, Pickard C J, Payne M C, Akhmatskaya E V, Nobes R H 2000 Int. J. Quant. Chem. 77 895
[25] Hamann D R, Schlter M, Chiang C 1979 Phys. Rev. Lett. 43 1494
[26] Clark S J, Segall M D, Pickard C J, Hasnip P J, Probert M I, Refson K, Payne M C 2005 Zeitschrift fr Kristallographie 220 567
[27] Gonze X, Allan D C, Teter M P 1992 Phys. Rev. Lett. 68 3603
[28] Gonze X, Beuken J M, Caracas R, Detraux F, Fuchs M, Rignanese G M, Sindic L, Verstraete M, Zerah G, Jollet F, Torrent M, Roy A, Mikami M, Ghosez P, Raty J Y, Allan D C 2002 Comput. Mater. Sci. 25 478
[29] Monkhorst H J, Pack J D 1976 Phys. Rev. B 13 5188
[30] Born M, Huang K 1954 Dynamical Theory of Crystal Lattices (Oxford: Oxford University Press) p121
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[1] Chu J R, Huang W H, Maedac R，Itoh T, Suga T 2001 Chin. Phys. 10 167
[2] Li G R, Zhang L N, Wang T B, Ding A L, Zhao S C 2006 Acta Phys. Sin. 55 3711 (in Chinese) [李国荣, 张丽娜, 王天宝, 丁爱丽, 赵苏串 2006 55 3711]
[3] Takenaka T, Nagata H 2005 J. Eur. Ceram. Soc. 25 2693
[4] Takenaka T, Maruyama K I, Sakata K 1991 Jpn. J. Appl. Phys. 30 2236
[5] Jiang X P, Li L Z, Zeng M, Chan H L W 2006 Mater. Lett. 60 1786
[6] Davies M, Aksel E, Jones J L 2011 J. Am. Ceram. Soc. 94 1314
[7] Aksel E, Forrester J S, Kowalski B, Deluca M, Damjanovic D, Jones J L 2012 Phys. Rev. B 85 024121
[8] Lei N, Zhu M, Yang P, Wang L, Wang L, Hou Y, Yan H 2011 J. Appl. Phys. 109 054102
[9] Zhang Y R, Li J F, Zhang B P, Peng C E 2008 J. Appl. Phys. 103 074109
[10] Liu H, Ge W, Jiang X, Zhao X, Luo H 2008 Mater. Lett. 62 2721
[11] Ge W W, Li J F, Viehland D, Luo H S 2010 J. Am. Ceram. Soc. 93 1372
[12] Zhou J, Peng W W, Zhang D, Yang X Y, Chen W 2008 Comput. Mater. Sci. 44 67
[13] Niranjan M K, Karthik T, Asthana S, Pan J, Waghmare U V 2013 J. Appl. Phys. 113 194106
[14] Vakhrushev S B, Isupov V A, Kvyatkovsky B E, Okuneva N M, Pronin I P, Smolensky G A, Syrnikov P P 1985 Ferroelectrics 63 153
[15] Zvirgzds J A, Kapostin P P, Zvirgzde J V, Kruzina T V 1982 Ferroelectrics 40 75
[16] Jones G O, Thomas P A 2002 Acta Crystallogr. B 58 168
[17] Isupov V A 2005 Ferroelectrics 315 123
[18] Park S E, Chung S J, Kim I T 1996 J. Am. Ceram. Soc. 79 1290
[19] Zhao M L, Zhong W L, Wang C L, Wang J F, Zhang P L 2002 Acta Phys. Sin. 51 1856 (in Chinese) [赵明磊, 钟维烈, 王春雷, 王矜奉, 张沛霖 2002 51 1856]
[20] Kreisel J, Glazer A M, Jones G, Thomas P A, Abello L, Lucazeau G 2000 J. Phys.: Condens. Matter 12 3267
[21] Chen W, Li Y, Xu Q, Zhou J 2005 J. Electroceram. 15 229
[22] Sun R, Lin D I, Zhang Q, Fang B, Zhang H, Li X, Wang S, Wang D, Zhao X, Luo H 2011 J. Adv. Dielect. 1 237
[23] Ming B Q, Wang J F, Zang G Z 2008 Chin. Phys. Lett. 25 3776
[24] Milman V, Winkler B, White J A, Pickard C J, Payne M C, Akhmatskaya E V, Nobes R H 2000 Int. J. Quant. Chem. 77 895
[25] Hamann D R, Schlter M, Chiang C 1979 Phys. Rev. Lett. 43 1494
[26] Clark S J, Segall M D, Pickard C J, Hasnip P J, Probert M I, Refson K, Payne M C 2005 Zeitschrift fr Kristallographie 220 567
[27] Gonze X, Allan D C, Teter M P 1992 Phys. Rev. Lett. 68 3603
[28] Gonze X, Beuken J M, Caracas R, Detraux F, Fuchs M, Rignanese G M, Sindic L, Verstraete M, Zerah G, Jollet F, Torrent M, Roy A, Mikami M, Ghosez P, Raty J Y, Allan D C 2002 Comput. Mater. Sci. 25 478
[29] Monkhorst H J, Pack J D 1976 Phys. Rev. B 13 5188
[30] Born M, Huang K 1954 Dynamical Theory of Crystal Lattices (Oxford: Oxford University Press) p121
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