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PublicouJoão Carlos krause Alterado mais de 3 anos atrás

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D.J.Gonsiorkiewicz* 1, J.C.Krause 1, A. V. dos Santos 1 and C. Paduani 2 1 URI – Santo Ângelo- RS - Brazil 2 UFSC – Florianópolis – SC - Brazil Investigation of the magnetic properties of substituted iron nitrides Fe 3 MN, M=Li, Be, Sm e Gd. Bibliografia: [1] E. L. Peltzer y Blancá, J. Desimoni,, N. E. Christensen, H. Emmerich, S. Cottenier, The magnetization of γ′-Fe4N: theory vs. experiment. Physica Status Solidi B 246, No. 5, 909–928, 2009. [2] C. Paduani, Electronic structure of the perovskite-type nitride RuFe3N, Journal of Magnetism and Magnetic Materials. 278, 231–236, 2004. [3] A.N. Timshevskii, V.A. Timoshevxkii, B.Z. Yanchitsky, V.A. Yavna, Electronic structure, hyperfine interactions and disordering affects in iron nitride Fe 4 N. Computacional Materials Science, 22, 99-105, 2001. [4] P. Blaha, K.Schwarz, G. Madsen, D. Kvasnicka, J. Luitz. WIEN2k - An Augmented Plane Wave Plus Local Orbitals Program for Calculating Crystal Properties - User’s Guide. October, 2009. Abstract The linearized augmented plane wave (LAPW) method as implemented in the WIEN2K code is used to investigate the electronic structure of the ferromagnetic compound '-Fe4N (fcc) with the substitution of Be, Li, Sm and Gd for Fe at FeI (corner) sites. The total energy is calculated in several cell volumes for each compound to determine their stability. From the calculations are obtained the magnetic moments, density of states (DOS) and electronic density at the equilibrium volume. Electronic structure calculations were performed for the Fe 4 N compound, for which it was obtained a lattice parameter of 3.8072 Å (consistent with the literature), as well as for the compounds BeFe 3 N, LiFe 3 N, SmFe 3 N and GdFe 3 N. From calculations of the densities of states we observed for both these compounds a strong interaction between Fe atoms with N atoms, whereas the interaction of N atoms with the impurity atoms (Be and Li) is very weak. In the compounds SmFe3N and GdFe3N similar interactions were also observed through hybridizations with the p orbitals of the substituents. The results indicate that both compounds can be formed in stable fcc structure. Objectives Investigate through DFT calculations the stability, magnetic properties, electronic densities and density of states in '-type nitrides (Fe 4-X M X N, where M = Be, Li, Sm and Gd). Methodology First the equilibrium lattice parameter was calculated for the '-Fe 4 N compound. With the same unit cell of '-Fe 4 N calculations were performed for the properties of the BeFe 3 N, LiFe 3 N, SmFe 3 N and GdFe 3 N compounds. The space group used is P (cubic cell), and beryllium, lithium, samarium or gadolinium were inserted at the corner sites in the perovskite structure. Table 1: Data entered into the WIEN2K to calculate the electronic properties of Fe 4 N. Results The equilibrium lattice parameters obtained are: 3.8033 Å for Fe 4 N, 3.6981 Å for BeFe 3 N, 3.7872 Å for LiFe 3 N, 4,23 Å for SmFe 3 N and 4,02Å for GdFe 3 N. Electronic densities of states demonstrate for both compounds, BeFe 3 N and LiFe 3 N, strong interactions between the d orbitals of the Fe atoms with the s orbitals of the N atoms, and the interaction of the impurities is very weak. For the and SmFe3N GdFe3N compounds were observed hybridization between the orbitals of iron and nitrogen with the substituents (Sm or Gd). For the magnetic moment we obtained the following results: 10.41 µ B for Fe 4 N, 4.68 µ B for BeFe 3 N, 7.30 µ B for LiFe 3 N, -1.06551µ B for SmFe 3 N and 7.44148µ B GdFe 3 N. Conclusion The results show that the lattice parameter, for the compounds containing Li and Be, decreases with the insertion of impurity atoms, and it increases with the substitution of Sm e Gd. From the density of States we see strong interactions between the iron atoms and nitrogen atoms, whereas the interactions with lithium or beryllium are very weak. With Sm and Gd we observed strong interactions with nitrogen. The magnetic moments decrease of this with the insertion of substituents, and an antiferromagnetic behavior was identified for the samarium compound. The calculations for the total energy show that these compounds can be experimentally, obtained but their stabilities are smaller than for -Fe 4 N. (a) (b) (c) (a)(b)(c) Figure 4: Density of states for the LiFe 3 N : (a) s, p and d states for Fe; (b) s and p states for N; (c) s and p states for Li. *PROBIC-FAPERGS Compound Lattice Parameter (Å) Space groupAtomic positions Atomic radius (a.u) Fe 4 N3.797 [1] Pm-3m (221) FeI (0.0,0.0,0.0) FeII x(0.5,0.5,0.0) y(0.5,0.0,0.5) z(0.0,0.5,0.5) N (0.5,0.5,0.5) Fe I: 2.0 FeII: 2.0 N: 1.38 Figure 5: Density of states for the SmFe 3 N : (a) s, p and d states for the Fe; (b) s and p states for N; (c) s states for Sm; (d) p states for Sm. (a)(b) (c) (d) (a)(b)(c) (d) Figure 6: Density of states for the GdFe 3 N : (a) s, p and d states for the Fe; (b) s and p states for N; (c) s states for Gd; (d) p states for Gd. Figure 1: Unit cell of perovskite structure. Figure 3: Density of states for the BeFe 3 N : (a) s, p and d states for Fe; (b) s and p states for N and (c) s and p states of Be. Figure 2: Total Energy curves for compounds.

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