In this work, we present a detailed study of the structural and the electronic structure of the double perovskite Ba2Er(Nb,Sb)O 6. All calculations were performed with the Full-Potential Linear Augmented Plane Wave method (FP-LAPW) based on the Density Functional Theory (DFT). From the minimization of energy as a function of volume using the Murnaghan's state equation has been obtained the equilibrium lattice parameter and the bulk modulus of these compounds. The study of the electronic structure was based in the analysis of the electronic density of states (DOS), and the density of charge, showing that these compounds have a total magnetic moment of 3.0 μB per formula unit due to Er atoms.Fil: Gil Rebaza, Arles Víctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Deluque Toro, Crispulo Enrique. Universidad Popular del Cesar; ColombiaFil: Téllez Landínez, D. A. Universidad Nacional de Colombia; ColombiaFil: Roa Rojas, J.. Universidad Nacional de Colombia; Colombi

Deluque Toro, Crispulo Enrique

Gil Rebaza, Arles Víctor

Roa Rojas, J.

Téllez Landínez, D. A

Journal of Physics Conference Series

English

LAReferencia - Red Federada de Repositorios Institucionales de Publicaciones Científicas Latinoamericanas

This content has been downloaded from IOPscience. Please scroll down to see the full text.Download details:IP Address: 181.165.255.126This content was downloaded on 02/04/2014 at 01:50Please note that terms and conditions apply.Electronic Structure of the Double Perovskite Ba2Er(Nb,Sb)O6View the table of contents for this issue, or go to the journal homepage for more2014 J. Phys.: Conf. Ser. 480 012041(http://iopscience.iop.org/1742-6596/480/1/012041)Home Search Collections Journals About Contact us My IOPscience      Electronic Structure of the Double Perovskite Ba2Er(Nb,Sb)O6 A. V. Gil Rebaza1, C.E. Deluque Toro2, D.A. Landínez Téllez3 and J. Roa-Rojas3  1 Depto. de Física, Facultad de Ciencias Exactas - UNLP, Instituto de Física La Plata IFLP-CONICET, cc 67 (1900) La Plata, Argentina 2 Grupo de Nuevos Materiales, Departamento de Física, Universidad Popular del Cesar, Valledupar, Colombia  3 Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997, Bogotá DC, Colombia   Received 4 October 2013, in final form XX Novembrer 2013 Abstract. In this work, we present a detailed study of the structural and the electronic structure of the double perovskite Ba2Er(Nb,Sb)O6. All calculations were performed with the Full-Potential Linear Augmented Plane Wave method (FP-LAPW) based on the Density Functional Theory (DFT). From the minimization of energy as a function of volume using the Murnaghan’s state equation has been obtained the equilibrium lattice parameter and the bulk modulus of these compounds. The study of the electronic structure was based in the analysis of the electronic density of states (DOS), and the density of charge, showing that these compounds have a total magnetic moment of 3.0 µB per formula unit due to Er atoms. 1.  Introduction Currently the complex perovskites with generic formula A2MM'O6 [1-3] have been subject of enhanced scientific studies because the wide range of applications that these materials present on an industrial scale, double perovskites belonging to the series Ba2LnB'O6 (Ln=lanthanide and Y3+ and B'=Nb5+, Ta5+, Sb5+) are of interest due to their potential use as substrates for high-Tc superconductors [4,5] and their likely high chemical compatibility with the structurally analogous, oxygen deficient double perovskites, Ba2LnSnO6-δ; a series of interest for use as solid state electrolytes due to their high ionic conductivity [6,7]. Substitution of Nb5+, Ta5+ or Sb5+ could provide a method of controlling the oxygen stoichiometry of these compounds, potentially minimizing the problems caused by reduction of Ba2LnSnO6-δ that is thought to be a consequence of the large level of oxygen vacancies in these compounds [6]. Phase transitions in perovskites have long been of interest to solid-state chemists [8].  Previous studies [9, 10], using laboratory X-ray and medium resolution neutron diffraction, reported that the structures in the series Ba2LnSbO6 change from R-3 rhombohedral (tilt system a-a-a-) to Fm-3m cubic (a0a0a0) symmetry with decreasing size of the Ln3+ cation. Conversely the niobate series Ba2LnNbO6 exhibits the sequence: I2/m monoclinic (a-a-c0), I4/m tetragonal (a0a0c-) to Fm-3m cubic symmetry. That the symmetry increase as the ionic radius of the lanthanide decreases, this is consistent with the increase of the tolerance factor t. An increase in the tolerance factor indicates that the volume of the BO6 octahedron is better matched to the size of the AO12 polyhedron reducing the need for the octahedral tilting to accommodate this A-site cation. Since octahedral tilting is 21st Latin American Symposium on Solid State Physics (SLAFES XXI) IOP PublishingJournal of Physics: Conference Series 480 (2014) 012041 doi:10.1088/1742-6596/480/1/012041Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Published under licence by IOP Publishing Ltd 1responsible for the lowering of the symmetry from cubic, the symmetry tends to increase as the B-type cation gets smaller. The aim of this work is to carry out a detailed ab initio theoretical study of the complex perovskites Ba2ErSbO6 and Ba2ErNbO6, which were experimentally  reported as cubic structures with spacial group Fm3m  [11-13]. Our calculations shown that these compounds have a total magnetic moment of 3.0 µB per formula unit due to Er atoms 2.  Computational Details  The calculations were performed using Full Potential Linearized Augmented Plane Wave (FP-LAPW) method, within the Density Functional Theory formalism [14], Wien2k code [15]. The exchange-correlation potential was described using the Perdew–Burke–Ernzerhof [16] expression, based in the Local Spin Density Approximation (LSDA) and Generalized Gradient Approximation (GGA) [17]. In all calculations, we used the next muffin-tin radius RMT(Ba)=2.5, RMT(Er)=2.3, RMT(Nb, Sb)=2.05 and RMT(O)=1.60 bohr; and the parameter RMT×Kmax was kept equal to 7 and Gmax = 12. The irreducible Brilloiun zone was described with 286 k-points, a mesh of 21×21×21. Furthermore, in all calculations we have considered spin polarization and the parameter of convergence was the variation of charge 10-5 a.u., the core and valence states are treated in the fully and scalar relativistic scheme, respectively. In the present work, we have considered these compounds with cubic crystalline structure Fm-3m (225), see Figure 1.        Figure 1: Cubic crystal structure Fm-3m of the compound Ba2(Nb,Sb)ErO6.  3.  Results and discussion   In order to obtain the equilibrium structure, the total energy vs. lattice parameter curves were obtained for BaEr(Nb,Sb)O compounds using LSDA and GGA. These curves were fitted using the Birch-Murnaghan’s state equation [18] to determine the equilibrium lattice parameters (a), bulk modulus (B) and their derivate (B’). In Table 1 we shows these values together experimental data obtained from the bibliography [11-13]. For both compounds the ground state belong to GGA calculations, where the a value for these compounds are in agree with experimental one.  Table 1: Theoretical value of a (Å), B (GPa) and B’ of the compound Ba2Er(Nb,Sb)O6.    a (Å) B (GPa) B’ Ba2ErNbO6 LDA 8.3176 161.3 5.1  GGA 8.4956 131.2 5.6  Exp. 8.4270[11] 8.4193[12]   Ba2ErSbO6 LDA 8.3124 146.7 3.9  GGA 8.5048 123.8 5.9  Exp. 8.3960[12] 8.3904[13]   21st Latin American Symposium on Solid State Physics (SLAFES XXI) IOP PublishingJournal of Physics: Conference Series 480 (2014) 012041 doi:10.1088/1742-6596/480/1/0120412  Figure 2: Total density of states and projected per atom of the compound  (a) Ba2ErNbO6 and (b) Ba2ErSbO6.  In figure 2, we show the total density of states (D.O.S.) of these compounds where and by atom. In both compounds the DOS belong to Ba atoms are locate in depth energies values without any hybridization with other atomic orbitals. Between -6.0 and -4.0 eV there are hybridization between the 4d-(Nb, Sb) and the 2p-O orbitals whereas between -4.0 and -1.5 eV we found hybridization of the 2p-O and 4f-Er orbital, but only in the majority DOS. Only in the Ba2ErSbO6 compound is possible see a hybridization 5s-Sb and 2s-O orbitals. In both compounds, the DOS of the Er atom show a dislocation and different population between the majority and minority DOS, producing a magnetic moment in this atom close to 2.86 µB. In the figure 3, we show the difference of the density of charge up and down in the plane (100) for both compounds, where is possible to see a mayor concentration of this difference around to the Er atoms, showing the magnetic character of these atoms. This is the reason why these compounds have a magnetic ground state with a magnetization of 3.0 µB per formula unit, agreeing with experimental studies for the case of the Ba2ErSbO6 [13].      Figure 3: Difference between the charge density up and down in the plane (100) of the (a) Ba2ErNbO6 and (b) Ba2ErSbO6. -28-14014-12 -8 -4 0 4-28-1401428 (b)   Total Ba  Er Nb  O(a) D.O.S.Energy (eV) Total Ba  Er Sb  O21st Latin American Symposium on Solid State Physics (SLAFES XXI) IOP PublishingJournal of Physics: Conference Series 480 (2014) 012041 doi:10.1088/1742-6596/480/1/0120413 4.  Conclusions The structural and electronic properties of the Ba2Er(Nb,Sb)O6 perovskite compound in the cubic structures were calculated using the method of Linearized Augmented Plane Wave on the Generalized Gradient (GGA) and Local Density (LDA) approximations with similar results. By minimizing the energy as a function of volume, structural characteristics such as the total energy, the equilibrium volume, the volume module, and the lattice parameters that minimize energy of the system were determined, where the equilibrium lattice parameter is in agree with experimental data. Furthermore, from analysis of the DOS and the density of charge, was possible explain the magnetic ground state of these compound, with a magnetization of 3.0 µB per formula unit due mainly to the contribution of Er atom. Acknowledgments This work was supported in part by the Universidad Popular del Cesar.   References [1] L.T. Corredor, J. Roa-Rojas, D.A. Landínez Téllez, R. Beltrán, P. Pureur, F. Mesquita, J. Albino Aguiar 2013 J. Appl. Phys. 113 17E302 [2] D.P. Llamosa, D.A. Landínez Téllez, J. Roa-Rojas 2009 Physica B 404 2726 [3] R.B. Macquart, Q.D. Zhou, B.J. Kennedy 2009 Journal of Solid State Chem. 7 1691 [4] A.M. Glazer 1972 Acta Crystallogr. Sect. B 28 3384 [5] A.M. Glazer 1975 Acta Crystallogr. Sect. A 31 756 [6] P.M. Woodward 1997 Acta Crystallogr. Sect. B 53 32 [7] C.J. Howard, B.J. Kennedy, P.M. Woodward 2003 Acta Crystallogr. B 59 463 [8] M. Wakeshima, D. Harada, Y. Hinatsu 1999 J. Alloy and Compd. 287 130 [9] M. Wakeshima, D. Harada, Y. Hinatsu, N. Masaki 1999 J. Solid State Chem. 47 618 [10] M. Wakeshima, D. Harada, Y. Hinatsu 2000 J. Mater. Chem. 10 419 [11] F.S. Galasso, Structure, Properties and Preparation of Perovskite-type Compounds, Pergamon Press, Oxford 1969 [12] P. J. Saines, B. J. Kennedy, M. M. Elcombe 2007 J Solid State Chem. 180 401 [13] S. Calder, T. Fennell, W. Kochelmann, G. C. Lau, R. J. Cava, S. T. Bramwell 2010 J. Phys.: Condens. Matter 22 116007 [14] P. Hohenberg, W. Kohn 1964 Phys. Rev. 136 864 [15] P. Blaha, K. Schwarz, G.K.H. Madsen, D. Kvasnicka, J. Luitz, WIEN2k_11.1, Techn. Universitat Wien, Austria, 2001 [16] J.P. Perdew, Y. Wang 1992 Phys. Rev. B. 45 13244 [17] J.P. Perdew, S. Burke, M. Ernzerhof 1996 Phys. Rev. Lett. 77 3865 [18] F. D. Murnaghan 1944 Proc. Natl. Acad. Sci., USA. 30 244 21st Latin American Symposium on Solid State Physics (SLAFES XXI) IOP PublishingJournal of Physics: Conference Series 480 (2014) 012041 doi:10.1088/1742-6596/480/1/0120414

Electronic structure of the double perovskite Ba2Er(Nb,Sb)O 6

CONICET Digital

A V Gil Rebaza

C E Deluque Toro

D A Landínez Téllez

J Roa-Rojas

Crossref

Electronic Structure of the Double Perovskite Ba<sub>2</sub>Er(Nb,Sb)O<sub>6</sub>

In this work, we present a detailed study of the structural and the electronic structure of the double perovskite Ba2Er(Nb,Sb)O6. All calculations were performed with the Full-Potential Linear Augmented Plane Wave method (FP-LAPW) based on the Density Functional Theory (DFT). From the minimization of energy as a function of volume using the Murnaghan's state equation has been obtained the equilibrium lattice parameter and the bulk modulus of these compounds. The study of the electronic structure was based in the analysis of the electronic density of states (DOS), and the density of charge, showing that these compounds have a total magnetic moment of 3.0 μB per formula unit due to Er atoms.Instituto de Física La Plat

Deluque Toro, C. E.

Landínez Téllez, D. A.

      Electronic Structure of the Double Perovskite Ba2Er(Nb,Sb)O6 A. V. Gil Rebaza1, C.E. Deluque Toro2, D.A. Landínez Téllez3 and J. Roa-Rojas3  1 Depto. de Física, Facultad de Ciencias Exactas - UNLP, Instituto de Física La Plata IFLP-CONICET, cc 67 (1900) La Plata, Argentina 2 Grupo de Nuevos Materiales, Departamento de Física, Universidad Popular del Cesar, Valledupar, Colombia  3 Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997, Bogotá DC, Colombia   Received 4 October 2013, in final form XX Novembrer 2013 Abstract. In this work, we present a detailed study of the structural and the electronic structure of the double perovskite Ba2Er(Nb,Sb)O6. All calculations were performed with the Full-Potential Linear Augmented Plane Wave method (FP-LAPW) based on the Density Functional Theory (DFT). From the minimization of energy as a function of volume using the Murnaghan’s state equation has been obtained the equilibrium lattice parameter and the bulk modulus of these compounds. The study of the electronic structure was based in the analysis of the electronic density of states (DOS), and the density of charge, showing that these compounds have a total magnetic moment of 3.0 µB per formula unit due to Er atoms. 1.  Introduction Currently the complex perovskites with generic formula A2MM'O6 [1-3] have been subject of enhanced scientific studies because the wide range of applications that these materials present on an industrial scale, double perovskites belonging to the series Ba2LnB'O6 (Ln=lanthanide and Y3+ and B'=Nb5+, Ta5+, Sb5+) are of interest due to their potential use as substrates for high-Tc superconductors [4,5] and their likely high chemical compatibility with the structurally analogous, oxygen deficient double perovskites, Ba2LnSnO6-δ; a series of interest for use as solid state electrolytes due to their high ionic conductivity [6,7]. Substitution of Nb5+, Ta5+ or Sb5+ could provide a method of controlling the oxygen stoichiometry of these compounds, potentially minimizing the problems caused by reduction of Ba2LnSnO6-δ that is thought to be a consequence of the large level of oxygen vacancies in these compounds [6]. Phase transitions in perovskites have long been of interest to solid-state chemists [8].  Previous studies [9, 10], using laboratory X-ray and medium resolution neutron diffraction, reported that the structures in the series Ba2LnSbO6 change from R-3 rhombohedral (tilt system a-a-a-) to Fm-3m cubic (a0a0a0) symmetry with decreasing size of the Ln3+ cation. Conversely the niobate series Ba2LnNbO6 exhibits the sequence: I2/m monoclinic (a-a-c0), I4/m tetragonal (a0a0c-) to Fm-3m cubic symmetry. That the symmetry increase as the ionic radius of the lanthanide decreases, this is consistent with the increase of the tolerance factor t. An increase in the tolerance factor indicates that the volume of the BO6 octahedron is better matched to the size of the AO12 polyhedron reducing the need for the octahedral tilting to accommodate this A-site cation. Since octahedral tilting is 21st Latin American Symposium on Solid State Physics (SLAFES XXI) IOP PublishingJournal of Physics: Conference Series 480 (2014) 012041 doi:10.1088/1742-6596/480/1/012041Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Published under licence by IOP Publishing Ltd 1responsible for the lowering of the symmetry from cubic, the symmetry tends to increase as the B-type cation gets smaller. The aim of this work is to carry out a detailed ab initio theoretical study of the complex perovskites Ba2ErSbO6 and Ba2ErNbO6, which were experimentally  reported as cubic structures with spacial group Fm3m  [11-13]. Our calculations shown that these compounds have a total magnetic moment of 3.0 µB per formula unit due to Er atoms 2.  Computational Details  The calculations were performed using Full Potential Linearized Augmented Plane Wave (FP-LAPW) method, within the Density Functional Theory formalism [14], Wien2k code [15]. The exchange-correlation potential was described using the Perdew–Burke–Ernzerhof [16] expression, based in the Local Spin Density Approximation (LSDA) and Generalized Gradient Approximation (GGA) [17]. In all calculations, we used the next muffin-tin radius RMT(Ba)=2.5, RMT(Er)=2.3, RMT(Nb, Sb)=2.05 and RMT(O)=1.60 bohr; and the parameter RMT×Kmax was kept equal to 7 and Gmax = 12. The irreducible Brilloiun zone was described with 286 k-points, a mesh of 21×21×21. Furthermore, in all calculations we have considered spin polarization and the parameter of convergence was the variation of charge 10-5 a.u., the core and valence states are treated in the fully and scalar relativistic scheme, respectively. In the present work, we have considered these compounds with cubic crystalline structure Fm-3m (225), see Figure 1.        Figure 1: Cubic crystal structure Fm-3m of the compound Ba2(Nb,Sb)ErO6.  3.  Results and discussion   In order to obtain the equilibrium structure, the total energy vs. lattice parameter curves were obtained for BaEr(Nb,Sb)O compounds using LSDA and GGA. These curves were fitted using the Birch-Murnaghan’s state equation [18] to determine the equilibrium lattice parameters (a), bulk modulus (B) and their derivate (B’). In Table 1 we shows these values together experimental data obtained from the bibliography [11-13]. For both compounds the ground state belong to GGA calculations, where the a value for these compounds are in agree with experimental one.  Table 1: Theoretical value of a (Å), B (GPa) and B’ of the compound Ba2Er(Nb,Sb)O6.    a (Å) B (GPa) B’ Ba2ErNbO6 LDA 8.3176 161.3 5.1  GGA 8.4956 131.2 5.6  Exp. 8.4270[11] 8.4193[12]   Ba2ErSbO6 LDA 8.3124 146.7 3.9  GGA 8.5048 123.8 5.9  Exp. 8.3960[12] 8.3904[13]   21st Latin American Symposium on Solid State Physics (SLAFES XXI) IOP PublishingJournal of Physics: Conference Series 480 (2014) 012041 doi:10.1088/1742-6596/480/1/0120412  Figure 2: Total density of states and projected per atom of the compound  (a) Ba2ErNbO6 and (b) Ba2ErSbO6.  In figure 2, we show the total density of states (D.O.S.) of these compounds where and by atom. In both compounds the DOS belong to Ba atoms are locate in depth energies values without any hybridization with other atomic orbitals. Between -6.0 and -4.0 eV there are hybridization between the 4d-(Nb, Sb) and the 2p-O orbitals whereas between -4.0 and -1.5 eV we found hybridization of the 2p-O and 4f-Er orbital, but only in the majority DOS. Only in the Ba2ErSbO6 compound is possible see a hybridization 5s-Sb and 2s-O orbitals. In both compounds, the DOS of the Er atom show a dislocation and different population between the majority and minority DOS, producing a magnetic moment in this atom close to 2.86 µB. In the figure 3, we show the difference of the density of charge up and down in the plane (100) for both compounds, where is possible to see a mayor concentration of this difference around to the Er atoms, showing the magnetic character of these atoms. This is the reason why these compounds have a magnetic ground state with a magnetization of 3.0 µB per formula unit, agreeing with experimental studies for the case of the Ba2ErSbO6 [13].      Figure 3: Difference between the charge density up and down in the plane (100) of the (a) Ba2ErNbO6 and (b) Ba2ErSbO6. -28-14014-12 -8 -4 0 4-28-1401428 (b)   Total Ba  Er Nb  O(a) D.O.S.Energy (eV) Total Ba  Er Sb  O21st Latin American Symposium on Solid State Physics (SLAFES XXI) IOP PublishingJournal of Physics: Conference Series 480 (2014) 012041 doi:10.1088/1742-6596/480/1/0120413 4.  Conclusions The structural and electronic properties of the Ba2Er(Nb,Sb)O6 perovskite compound in the cubic structures were calculated using the method of Linearized Augmented Plane Wave on the Generalized Gradient (GGA) and Local Density (LDA) approximations with similar results. By minimizing the energy as a function of volume, structural characteristics such as the total energy, the equilibrium volume, the volume module, and the lattice parameters that minimize energy of the system were determined, where the equilibrium lattice parameter is in agree with experimental data. Furthermore, from analysis of the DOS and the density of charge, was possible explain the magnetic ground state of these compound, with a magnetization of 3.0 µB per formula unit due mainly to the contribution of Er atom. Acknowledgments This work was supported in part by the Universidad Popular del Cesar.   References [1] L.T. Corredor, J. Roa-Rojas, D.A. Landínez Téllez, R. Beltrán, P. Pureur, F. Mesquita, J. Albino Aguiar 2013 J. Appl. Phys. 113 17E302 [2] D.P. Llamosa, D.A. Landínez Téllez, J. Roa-Rojas 2009 Physica B 404 2726 [3] R.B. Macquart, Q.D. Zhou, B.J. Kennedy 2009 Journal of Solid State Chem. 7 1691 [4] A.M. Glazer 1972 Acta Crystallogr. Sect. B 28 3384 [5] A.M. Glazer 1975 Acta Crystallogr. Sect. A 31 756 [6] P.M. Woodward 1997 Acta Crystallogr. Sect. B 53 32 [7] C.J. Howard, B.J. Kennedy, P.M. Woodward 2003 Acta Crystallogr. B 59 463 [8] M. Wakeshima, D. Harada, Y. Hinatsu 1999 J. Alloy and Compd. 287 130 [9] M. Wakeshima, D. Harada, Y. Hinatsu, N. Masaki 1999 J. Solid State Chem. 47 618 [10] M. Wakeshima, D. Harada, Y. Hinatsu 2000 J. Mater. Chem. 10 419 [11] F.S. Galasso, Structure, Properties and Preparation of Perovskite-type Compounds, Pergamon Press, Oxford 1969 [12] P. J. Saines, B. J. Kennedy, M. M. Elcombe 2007 J Solid State Chem. 180 401 [13] S. Calder, T. Fennell, W. Kochelmann, G. C. Lau, R. J. Cava, S. T. Bramwell 2010 J. Phys.: Condens. Matter 22 116007 [14] P. Hohenberg, W. Kohn 1964 Phys. Rev. 136 864 [15] P. Blaha, K. Schwarz, G.K.H. Madsen, D. Kvasnicka, J. Luitz, WIEN2k_11.1, Techn. Universitat Wien, Austria, 2001 [16] J.P. Perdew, Y. Wang 1992 Phys. Rev. B. 45 13244 [17] J.P. Perdew, S. Burke, M. Ernzerhof 1996 Phys. Rev. Lett. 77 3865 [18] F. D. Murnaghan 1944 Proc. Natl. Acad. Sci., USA. 30 244 21st Latin American Symposium on Solid State Physics (SLAFES XXI) IOP PublishingJournal of Physics: Conference Series 480 (2014) 012041 doi:10.1088/1742-6596/480/1/0120414

El Servicio de Difusión de la Creación Intelectual

 
 
 
 
 
 
Electronic Structure of the Double Perovskite 
Ba2Er(Nb,Sb)O6 
A. V. Gil Rebaza1, C.E. Deluque Toro2, D.A. Landínez Téllez3 and J. Roa-Rojas3 
 
1 Depto. de Física, Facultad de Ciencias Exactas - UNLP, Instituto de Física La Plata IFLP-CONICET, cc 67 (1900) La Plata, Argentina 
2 Grupo de Nuevos Materiales, Departamento de Física, Universidad Popular del Cesar, Valledupar, Colombia  
3 Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997, Bogotá DC, Colombia 
 
 
Received 4 October 2013, in final form XX Novembrer 2013 
Abstract. In this work, we present a detailed study of the structural and the electronic structure 
of the double perovskite Ba2Er(Nb,Sb)O6. All calculations were performed with the Full-
Potential Linear Augmented Plane Wave method (FP-LAPW) based on the Density Functional 
Theory (DFT). From the minimization of energy as a function of volume using the 
Murnaghan’s state equation has been obtained the equilibrium lattice parameter and the bulk 
modulus of these compounds. The study of the electronic structure was based in the analysis of 
the electronic density of states (DOS), and the density of charge, showing that these 
compounds have a total magnetic moment of 3.0 µB per formula unit due to Er atoms. 
1.  Introduction 
Currently the complex perovskites with generic formula A2MM'O6 [1-3] have been subject of enhanced 
scientific studies because the wide range of applications that these materials present on an industrial scale, 
double perovskites belonging to the series Ba2LnB'O6 (Ln=lanthanide and Y3+ and B'=Nb5+, Ta5+, 
Sb5+) are of interest due to their potential use as substrates for high-Tc superconductors [4,5] and their 
likely high chemical compatibility with the structurally analogous, oxygen deficient double 
perovskites, Ba2LnSnO6-δ; a series of interest for use as solid state electrolytes due to their high ionic 
conductivity [6,7]. Substitution of Nb5+, Ta5+ or Sb5+ could provide a method of controlling the oxygen 
stoichiometry of these compounds, potentially minimizing the problems caused by reduction of 
Ba2LnSnO6-δ that is thought to be a consequence of the large level of oxygen vacancies in these 
compounds [6]. Phase transitions in perovskites have long been of interest to solid-state chemists [8].  
Previous studies [9, 10], using laboratory X-ray and medium resolution neutron diffraction, reported 
that the structures in the series Ba2LnSbO6 change from R-3 rhombohedral (tilt system a-a-a-) to Fm-
3m cubic (a0a0a0) symmetry with decreasing size of the Ln3+ cation. Conversely the niobate series 
Ba2LnNbO6 exhibits the sequence: I2/m monoclinic (a-a-c0), I4/m tetragonal (a0a0c-) to Fm-3m cubic 
symmetry. That the symmetry increase as the ionic radius of the lanthanide decreases, this is 
consistent with the increase of the tolerance factor t. An increase in the tolerance factor indicates that 
the volume of the BO6 octahedron is better matched to the size of the AO12 polyhedron reducing the 
need for the octahedral tilting to accommodate this A-site cation. Since octahedral tilting is 
21st Latin American Symposium on Solid State Physics (SLAFES XXI) IOP Publishing
Journal of Physics: Conference Series 480 (2014) 012041 doi:10.1088/1742-6596/480/1/012041
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution
of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Published under licence by IOP Publishing Ltd 1
responsible for the lowering of the symmetry from cubic, the symmetry tends to increase as the B-type 
cation gets smaller. 
The aim of this work is to carry out a detailed ab initio theoretical study of the complex perovskites 
Ba2ErSbO6 and Ba2ErNbO6, which were experimentally  reported as cubic structures with spacial 
group Fm3m  [11-13]. Our calculations shown that these compounds have a total magnetic moment of 
3.0 µB per formula unit due to Er atoms 
2.  Computational Details  
The calculations were performed using Full Potential Linearized Augmented Plane Wave (FP-LAPW) 
method, within the Density Functional Theory formalism [14], Wien2k code [15]. The exchange-
correlation potential was described using the Perdew–Burke–Ernzerhof [16] expression, based in the 
Local Spin Density Approximation (LSDA) and Generalized Gradient Approximation (GGA) [17]. In 
all calculations, we used the next muffin-tin radius RMT(Ba)=2.5, RMT(Er)=2.3, RMT(Nb, Sb)=2.05 and 
RMT(O)=1.60 bohr; and the parameter RMT×Kmax was kept equal to 7 and Gmax = 12. The irreducible 
Brilloiun zone was described with 286 k-points, a mesh of 21×21×21. Furthermore, in all calculations 
we have considered spin polarization and the parameter of convergence was the variation of charge 10-
5 a.u., the core and valence states are treated in the fully and scalar relativistic scheme, respectively. 
In the present work, we have considered these compounds with cubic crystalline structure Fm-3m 
(225), see Figure 1. 
 
 
 
 
 
 
 
Figure 1: Cubic crystal structure Fm-3m of the 
compound Ba2(Nb,Sb)ErO6. 
 
3.  Results and discussion  
 
In order to obtain the equilibrium structure, the total energy vs. lattice parameter curves were 
obtained for BaEr(Nb,Sb)O compounds using LSDA and GGA. These curves were fitted using the 
Birch-Murnaghan’s state equation [18] to determine the equilibrium lattice parameters (a), bulk 
modulus (B) and their derivate (B’). In Table 1 we shows these values together experimental data 
obtained from the bibliography [11-13]. For both compounds the ground state belong to GGA 
calculations, where the a value for these compounds are in agree with experimental one. 
 
Table 1: Theoretical value of a (Å), B (GPa) and B’ of the compound Ba2Er(Nb,Sb)O6. 
 
  a (Å) B (GPa) B’ 
Ba2ErNbO6 LDA 8.3176 161.3 5.1 
 GGA 8.4956 131.2 5.6 
 Exp. 8.4270[11] 
8.4193[12] 
  
Ba2ErSbO6 LDA 8.3124 146.7 3.9 
 GGA 8.5048 123.8 5.9 
 Exp. 8.3960[12] 
8.3904[13] 
  
21st Latin American Symposium on Solid State Physics (SLAFES XXI) IOP Publishing
Journal of Physics: Conference Series 480 (2014) 012041 doi:10.1088/1742-6596/480/1/012041
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Figure 2: Total density of states and projected per atom of the compound  
(a) Ba2ErNbO6 and (b) Ba2ErSbO6. 
 
In figure 2, we show the total density of states (D.O.S.) of these compounds where and by atom. In 
both compounds the DOS belong to Ba atoms are locate in depth energies values without any 
hybridization with other atomic orbitals. Between -6.0 and -4.0 eV there are hybridization between the 
4d-(Nb, Sb) and the 2p-O orbitals whereas between -4.0 and -1.5 eV we found hybridization of the 2p-
O and 4f-Er orbital, but only in the majority DOS. Only in the Ba2ErSbO6 compound is possible see a 
hybridization 5s-Sb and 2s-O orbitals. In both compounds, the DOS of the Er atom show a dislocation 
and different population between the majority and minority DOS, producing a magnetic moment in 
this atom close to 2.86 µB. In the figure 3, we show the difference of the density of charge up and 
down in the plane (100) for both compounds, where is possible to see a mayor concentration of this 
difference around to the Er atoms, showing the magnetic character of these atoms. This is the reason 
why these compounds have a magnetic ground state with a magnetization of 3.0 µB per formula unit, 
agreeing with experimental studies for the case of the Ba2ErSbO6 [13].   
 
 
 
Figure 3: Difference between the charge density up and down in the plane (100) 
of the (a) Ba2ErNbO6 and (b) Ba2ErSbO6. 
-28
-14
0
14
-12 -8 -4 0 4
-28
-14
0
14
28 (b)
 
 
 Total
 Ba  Er
 Nb  O
(a)
 
D
.O
.S
.
Energy (eV)
 Total
 Ba  Er
 Sb  O
21st Latin American Symposium on Solid State Physics (SLAFES XXI) IOP Publishing
Journal of Physics: Conference Series 480 (2014) 012041 doi:10.1088/1742-6596/480/1/012041
3
 4.  Conclusions 
The structural and electronic properties of the Ba2Er(Nb,Sb)O6 perovskite compound in the cubic 
structures were calculated using the method of Linearized Augmented Plane Wave on the Generalized 
Gradient (GGA) and Local Density (LDA) approximations with similar results. By minimizing the 
energy as a function of volume, structural characteristics such as the total energy, the equilibrium 
volume, the volume module, and the lattice parameters that minimize energy of the system were 
determined, where the equilibrium lattice parameter is in agree with experimental data. Furthermore, 
from analysis of the DOS and the density of charge, was possible explain the magnetic ground state of 
these compound, with a magnetization of 3.0 µB per formula unit due mainly to the contribution of Er 
atom. 
Acknowledgments 
This work was supported in part by the Universidad Popular del Cesar.  
 
References 
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[14] P. Hohenberg, W. Kohn 1964 Phys. Rev. 136 864 
[15] P. Blaha, K. Schwarz, G.K.H. Madsen, D. Kvasnicka, J. Luitz, WIEN2k_11.1, Techn. Universitat 
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21st Latin American Symposium on Solid State Physics (SLAFES XXI) IOP Publishing
Journal of Physics: Conference Series 480 (2014) 012041 doi:10.1088/1742-6596/480/1/012041
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Electronic structure of the double perovskite Ba2Er(Nb,Sb)O 6

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