SEMICONDUCTOR MATERIALS

Effect of relaxation on the energetics and electronic structure of clean Ag3PO4(111) surface

Xinguo Ma1, 2, , Jie Yan1, Na Liu1, Lin Zhu1, Bei Wang1, Chuyun Huang1, 2 and Hui Lü1, 2

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 Corresponding author: Ma Xinguo, Email:maxg2013@sohu.com

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Abstract: The effect of relaxation on the energetics and electronic structure of clean Ag3PO4(111) surface has been studied, carried out using first-principles density functional theory(DFT) incorporating the GGA+U formalism. After atomic relaxation of the Ag3PO4(111) surface, it is found that O atoms are exposed to the outermost surface, due to an inward displacement of more than 0.06 nm for the two threefold-coordinated Ag atoms and an outward displacement of about 0.004 nm for three O atoms in the sublayer. The atomic relaxations result in a large transfer of surface charges from the outermost layer to the inner layer, and the surface bonds have a rehybridization, which makes the covalence increase and thus causes the surface bonds to shorten. The calculated energy band structures and density of states of the Ag3PO4(111) surface present that the atomic relaxation narrows the valence band width 0.15 eV and increases the band gap width 0.26 eV. Meantime, the two surface peaks for the unrelaxed structure disappear at the top of the valence band and the bottom of the conduction band after the relaxed structure, which induces the transformation from a metallic to a semi-conducting characteristic.

Key words: silver orthophosphateatomic relaxationelectronic structureDFT



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Fig. 1.  (Color online) The unrelaxed (a) and relaxed (b) slab model of clean Ag$_{3}$PO$_{4}$(111) surface. Red, purple, and blue spheres represent O, P, and Ag atoms, respectively.

Fig. 2.  (Color online) The difference charge density contour maps of Ag$_{3}$PO$_{4}$ along (a) O-P-O and (b) O-Ag-O planes. The atom positions are labeled.

Fig. 3.  The variation of BG width, CB width and VB width of Ag$_{3}$PO$_{4}$(111) surface as the function of slab thickness with a 6 Å vacuum, respectively. Slab thickness is specified by the number of ionic layers (see Figure 1).

Fig. 4.  Total density of states of the bulk structure of Ag$_{3}$PO$_{4}$ (a), and Ag$_{3}$PO$_{4}$(111) surfaces for unrelaxed (b) and relaxed (c) models.

Fig. 5.  Partial density of states for the unrelaxed and relaxed Ag$_{3}$PO$_{4}$(111) surfaces. The origin of the energy scale is taken at the Fermi level, as the vertical dotted line indicates.

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Table 1.   Surface energy (J/m$^{2})$ and relaxation energy (eV) for 1 × 1 unit cell, the value in brackets is the surface energy of unrelaxed structure.

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Table 2.   Atom displacements of Ag$_{3}$PO$_{4}$(111) surface for 16- and 24-layer slabs with respect to the ideal bulk positions, and the differences of Mulliken charge population between unrelaxed and relaxed surface models.

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    Received: 11 July 2015 Revised: Online: Published: 01 March 2016

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      Xinguo Ma, Jie Yan, Na Liu, Lin Zhu, Bei Wang, Chuyun Huang, Hui Lü. Effect of relaxation on the energetics and electronic structure of clean Ag3PO4(111) surface[J]. Journal of Semiconductors, 2016, 37(3): 033001. doi: 10.1088/1674-4926/37/3/033001 X G Ma, J Yan, N Liu, L Zhu, B Wang, C Y Huang, H Lü. Effect of relaxation on the energetics and electronic structure of clean Ag3PO4(111) surface[J]. J. Semicond., 2016, 37(3): 033001. doi: 10.1088/1674-4926/37/3/033001.Export: BibTex EndNote
      Citation:
      Xinguo Ma, Jie Yan, Na Liu, Lin Zhu, Bei Wang, Chuyun Huang, Hui Lü. Effect of relaxation on the energetics and electronic structure of clean Ag3PO4(111) surface[J]. Journal of Semiconductors, 2016, 37(3): 033001. doi: 10.1088/1674-4926/37/3/033001

      X G Ma, J Yan, N Liu, L Zhu, B Wang, C Y Huang, H Lü. Effect of relaxation on the energetics and electronic structure of clean Ag3PO4(111) surface[J]. J. Semicond., 2016, 37(3): 033001. doi: 10.1088/1674-4926/37/3/033001.
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      Effect of relaxation on the energetics and electronic structure of clean Ag3PO4(111) surface

      doi: 10.1088/1674-4926/37/3/033001
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      Project supported by the National Natural Science Foundation of China(Nos.51472081, 51102150, 61106046), the Development Funds of Hubei Collaborative Innovation Center(Nos.HBSKFMS2014003, HBSKFMS2014011), and the Foundation for High-Level Talents(No.GCRC13014).

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      • Corresponding author: Ma Xinguo, Email:maxg2013@sohu.com
      • Received Date: 2015-07-11
      • Accepted Date: 2015-09-05
      • Published Date: 2016-01-25

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