Magnetic and electronic properties of Li-, Be-, B- and F- doped C3N4: Ab initio calculations

Accepted Manuscript Magnetic and electronic properties of Li-, Be-, B- and F- doped C3N4: Ab initio calculations Saadi Berri PII:

S2352-2143(17)30100-4

DOI:

10.1016/j.cocom.2017.08.004

Reference:

COCOM 86

To appear in:

Computational Condensed Matter

Received Date: 21 May 2017 Revised Date:

5 August 2017

Accepted Date: 9 August 2017

Please cite this article as: S. Berri, Magnetic and electronic properties of Li-, Be-, B- and F- doped C3N4: Ab initio calculations, Computational Condensed Matter (2017), doi: 10.1016/j.cocom.2017.08.004. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Magnetic and electronic properties of Li-, Be-, B- and F- doped C3N4: ab initio calculations

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Saadi Berri Laboratory for Developing New Materials and their Characterizations, University of Setif 1,

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Algeria.

Abstract

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The structural, electronic and magnetic properties of Li, Be, B and F-doped carbon nitrides with β-C3N4, defect zinc-blende and tetragonal structure are studied by using firstprinciple's method. The investigation was done using the (FPLAPW) method where the exchange-correlation potential was calculated with the frame of GGA by Perdew et al. (Phys. Rev. Lett. 77 (1996) 3865). The possibility of half-metallic ferromagnetism in Li, Be, B and

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F-doped C3N4 were analyzed by electronic band structure and density of states calculations. We found that FC5N8 monoclinic and BeC5N8 tetragonal phase exhibits a complete half-

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metallic characteristic with a total spin moment of 1.00µ B and 3.00µ B, and energy band gap of (Eg ↓ =0.5eV) and (Eg ↑ =2.6 eV), respectively. These results may be of interest for

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spintronic applications.

Keywords: C3N4; Magnetic properties; Ab initio calculations; Electronic structure.

Author: E-mail : [email protected]

1.Introduction 1

ACCEPTED MANUSCRIPT Numerous investigations have been extensively done regarding carbon nitrides C3N4 with different compositions and structures, motivated by their material harder than has diamond [1, 2]. Recently, carbon nitrides C3N4 attracted attention due to their potential applications in photocatalysis [3], photodegradation [4] and photoelectrochemical Very recently, a novel metal – free semiconductor

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anticorrosion technology [5].

photocatalyst, carbon nitride, was found to have good performance in the photooxidation of methyl orange, the developed graphitic carbon nitride (g-C3N4) metalincluding compounds

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could effectively degrade MO dyes [6, 7]. Teter and Hemley [8] studied five types of C3N4, including α-C3N4, β-C3N4, cubic-C3N4, pseudocubic-C3N4 and g-C3N4.

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Graphitic-C3N4 was reported to be stable at ambient pressure [8-10], with band gap in the 2.6–3.0 eV range for energy, solar, and light-emitting diode (LED) materials. However, it is important to note the recent advances in the felds of AlInN and InGaN compound have been widely implemented in solar cells[11,12] thermoelectricity, [13,14] and LEDs. [15-19].

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Several publications in recent years have highlighted the effectiveness of g-C3N4 as a photo catalyst in areas such as the selective oxidation of alcohols and hydrocarbons [20, 21], and as a good photo catalytic performer in relation to hydrogen or oxygen production via water

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splitting with the use of visible light irradiation [22]. After a period of research Gracia and Kroll [23] reported a new g-C3N4 nanotube, based on density-functional-theory calculations.

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Pan, et al. [24] studied the electronic structure of W-, Ti-, Cr-, Mn-, Co- and Ni- doped gC3N4 nanotube using first-principle calculations. Zhu, et al. [25] studied the electronic structure of halogen-doped monolayer g-C3N4 photocatalyst using pseudopotential plane wave method.

The aim of this work is to examine the electronic band structure of Li, Be, B and F doped carbon nitrides in both β-C3N4 (space group P-3), defect zinc-blende (space group P43m) and tetragonal (space group P-42m) phases, with emphasis on its derived properties. Such doped Li, Be, B and F atoms can change the local density state around the Fermi level. The 2

ACCEPTED MANUSCRIPT crystal structures of pure and partial substitution on C3N4 are shown in Figs. 1 and 2. The calculations are performed using ab initio full-potential linearized augmented plane wave (FPLAPW) within the density functional theory DFT within the generalized gradient approximation GGA. Our paper is organized as follows. The theoretical background is

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presented in Section 2. Results and discussion are presented in Section 3. A summary of the results is given in Section 4.

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2. Method of calculations

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Self-consistent FP-LAPW [26, 27] calculations on pure and partial substitution on C3N4 were carried outusing WIEN2k package [28]. Exchange-correlation effects are treated using generalized gradient approximation (GGA) as parameterized by Perdew et al. [29]. The Kohn-Sham equations are solved self-consistently using full-potential linearized augmented

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plane wave method. In the interstitial region, the plane wave cutoff value was imposed by the condition RMTKmax = 8, where Kmax is the plane wave cutoff and RMT is the smallest of all atomic sphere radii. The radii RMT of the muffin tins (MT) are chosen to be approximately

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proportional to the corresponding ionic radii. The following initial atomic configurations were employed: (N 2s2 2p3),(Be 2s2),(Li 1s2 2s1), (C 2s2 2p2), (B 2s2 2p1) and (F 2s2 2p5).Self-

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consistent calculations are considered to be converged when the total energy of the system is stable within 10−4 Ry. The convergence criteria for total energy and force are taken as 10−5 and 10−4 eV/Å, respectively. The valence wave functions inside the spheres are expanded up to lmax = 10 while the charge density was Fourier expanded up to Gmax =12. The MonkorstPack special k-points were performed using 2500 special k-points in the Brillouin zone for pure C3N4, and 700 k-points for XC5N8( X=Li, Be, B and F). 3. Results and discussion

3

ACCEPTED MANUSCRIPT The main objective in this work is to calculate the total energy as a function of the unit-cell volume around the equilibrium cell volume V0 in both β(space group P-3), defect zinc-blende (space group P43m), tetragonal( space group P-42m ) and cubic ( space group I-43d ) phases, Fig.3 presents the structural optimization curves obtained by using the FP-LAPW

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method; the results indicate that β-C3N4 phase is found to be energetically more favorable than defect zinc-blende, tetragonal and cubic phases. The calculated total energies are fitted to the Murnaghan equation of state (EOS) E–V [30], so as to determine the ground state

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properties, such as equilibrium lattice constant a(Å), bulk modulus B(GPa) and its pressure derivative B'. The calculated structural parameters of β-C3N4, defect zinc-blende, tetragonal

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and cubic phases are reported in Table 1. The optimal lattice parameter and the bulk modulus obtained by this procedure are in agreement with the experimental value [8, 31] and theorical data[32-34]. Note, that the stability of C3N4 phases as predicted by Dong et al. [35]. The electronic band structure and the density of states (DOS) of a material give

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important information about its electronic behavior. The calculated electronic band structures and total density of states in both β-C3N4 , defect zinc-blende, tetragonal and cubic phases along the high symmetry lines in the first Brillouin zone as shown in Fig. 4. The valence band

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maximum (VBM) is located at the Γ point, whereas the conduction band minimum (CBM) is located at the Γ point in β-C3N4, defect zinc-blende and tetragonal phases, and (ΓH) directions

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for cubic phase. The energy gap values obtained from the FP-LAPW approach are 2.68, 2.68, 2.90 and 3.47eV, respectively. This band structure is representative of wide gap pure C3N4 with gaps semiconductor (See Table 1). These calculated values are comparable with the value measured by means of UV–Vis spectroscopy, viz., 3.1 eV, for an amorphous powder built from s-triazine motifs [36]. Xu et al. [37] calculated the band edge potentials using a recently developed approach where quasi-particle effects are taken into account through GW approximation. The band-gap of α-C3N4, β-C3N4, cubic-C3N4, pseudocubic-C3N4, g-htriazine, g-o-triazine and g-h-heptazine are 5.49 eV, 4.85 eV, 4.30 eV, 4.13 eV, 2.97 eV, 4

ACCEPTED MANUSCRIPT 0.93 eV and 2.88 eV, respectively. Moreover, Dong et al [35], calculated the band gap using pseudopotential plane wave (PP-PW) method in the frame of generalized gradient approximation of the β-C3N4, Cm-C3N4, I‾42m-C3N4, I‾43d-C3N4, Cmc21-C3N4 structures are 3.78, 3.74, 2.75, 2.91 and 3.43 eV, respectively. However, electronic structure calculations

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have weaknesses as well. Most of the calculations are based on density functional theory in the GGA or LDA approximation. It is well known that these methods underestimate the band gap for many semiconductors and insulators, typically by 30%.

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In the next stage, we presented the total densities of states of Li, Be, B and F-doped β-C3N4, defect zinc-blende and tetragonal phase, in which the spin-up and spin-down sub-

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bands is shown in Figs. 5-7. One can observe the absence of a gap at Fermi level, for BC5N8 and LiC5N8 in Tetragonal, Orthorhombic and Monoclinic structure, BeC5N8 in Orthorhombic and Monoclinic structure, and FC5N8 in Tetragonal and Orthorhombic structure. In the case FC5N8 Monoclinic structure (Fig. 8), the majority-spin channel is metallic whereas in the

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minority-spin channel there is an energy gap around the Fermi level of about 0.50 eV. It is evident that the compound exhibits a half-metallic ferromagnetic band structure, the minority channel shows a gap at the Fermi energy. The half metallicity is originated by the

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hybridization of N- py and C-s with F-pz states. Moreover, orbital projected partial density of electronic states of atoms in our FC5N8 monoclinic structure are presented in Fig. 9, one can

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see the exchange splitting in the C-s with F-pz states, along with the fact that the C-s (spin-up) and F-pz (spin-up) states are occupied completely, while the N- py states are partially occupied. Actually, it is observed that the py orbitals of N atoms are located between -3 eV and -1 eV below EF, so it has no remarkable effect on bonding features of the systems. In the energy range between 1 to 3 eV, the band of F-py hybridized with F-px has no prominent effect on electronic structure of the system for both majority and minority states. Note that in the BeC5N8 Tetragonal structure ( Fig. 10), the metallic character of the minority-spin channel and semiconducting character of the majority-spin channel is similar to the HM 5

ACCEPTED MANUSCRIPT ferromagnetism of (2x2) g-C4N3 [38]. Therefore, the FC5N8 Monoclinic and BeC5N8 Tetragonal are a candidate matrial for future spintronic applications. The total magnetic moment contains two contributions one each from the nitrogen atoms and the interstitial region Table 2. The main contribution comes from the nitrogen

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atom, whereas the moments of the carbon are small. For the FC5N8, the magnetic moment is found to be 1 µB per formula unit, and it is evenly distributed among fluorine atoms, three neighboring nitrogen atoms and interstitial region in a monoclinic structure. The absence of

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the transition-metal atoms makes these compounds important model systems for the study of

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the origin and properties of the half-metallic ferromagnetism of s-p electron systems.

4. Conclusion

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The structural, electronic and magnetic properties of Li, Be, B and F-doped carbon nitrides with β-C3N4, defect zinc-blende and tetragonal phases are investigated by density functional theory with generalized gradient approximation GGA. The possibility of half-

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metallic ferromagnetism in Li, Be, B and F-doped C3N4 were analyzed by electronic band

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structure and density of states calculations. We found that FC5N8 monoclinic and BeC5N8 tetragonal phase exhibits a complete half-metallic characteristic with a total spin moment of 1.00µ B and 3.00µ B, and energy band gap of (Eg ↓ =0.5eV) and (Eg ↑ =2.6 eV), respectively. Therefore, these new materials are good candidates for potential applications in spintronic.

6

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[5] Y. Bu, Z. Chen, J. Yu, and W. Li. Electrochim. Acta 88 (2013) 294–300. [6] S. C. Yan, Z. S. Li, Z. G. Zou Langmuir 25 (2009) 10397.

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[11] E. C. Young, F. Wu, A. E. Romanov, D. A. Haeger, S. Nakamura, S. P. Denbaars, D. A. Cohen and J. S. Speck, Appl. Phys. Lett., 101 (2012) 5. [12] C. J. Neufeld, N. G. Toledo1, S. C. Cruz, M. Iza, S. P. DenBaars and U. K. Mishra,

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ACCEPTED MANUSCRIPT [20] Zhang, P.; Gong, Y.; Li, H.; Chen, Z.; Wang, Y. Selective oxidation of benzene to phenol by FeCl3/mpg-C3N4 hybrids. RSC Adv. 3 (2013) 5121–5126. [21] F. Su, S.C. Mathew, G. Lipner, X. Fu, M. Antonietti, S. Blechert, X. J. Wang. Am. Chem. Soc. 132 (2010) 16299–16301.

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[22] X. Wang, K. Maeda, A. Thomas, K. Takanabe, G. Xin, J.M. Carlsson, K. Domen, M.

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[25] Bicheng Zhu, Jinfeng Zhang, Chuanjia Jiang, Bei Cheng, Jiaguo Yu, Applied Catalysis

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Nordström, Efficient linearization of the augmented plane-wave method, Phys.Rev.B 64

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[28] P. Blaha, K. Schwarz, G. K. H. Madsen, D. Kvasnicka, J. Luitz, WIEN2K, an

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Augmented Plane Wave +Local orbitals program for calculating crystal properties (Karlheinz Schwarz, Technische Universität, Wien, Austria, 2001), ISBN 3-9501031-1-2.

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ACCEPTED MANUSCRIPT [33] J. Martin-Gil, F.J. Martin-Gil, M. Sarikaya, M. Qian, M. Jos-Yacamn, A. Rubio, Journal of Applied Physics 81 (6) (1997) 2555–2559. [34]P. Mori-Sánchez, M. Marqués, A. Beltrán, J.Z. Jiang, L. Gerward, J.M. Recio, Physical Review B 68 (6) (2003) 064115 (5).

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[37] Yuan Xu, Shang-Peng Gao. International Journal of Hydrogen Energy, 37 (15) (2012)

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11072–11080.

[38] Aijun Du, Stefano Sanvito and Sean C. Smith. Physical Review Letters 108 (2012)

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197207.

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ACCEPTED MANUSCRIPT Figure captions Fig. 1. Crystal structure of β-C3N4, defect zinc-blende, cubic and tetragonal phase. Fig. 2. Crystal structure of XC5N8(X= Li, Be, B and F). Fig. 3. Volume optimization for the C3N4.

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Fig. 4. Band structure and total densities of states for β- C3N4, defect zinc-blende, cubic and tetragonal phase.

Figs. 5. Spin-polarized total densities of states (TDOS) of tetragonal structure.

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Figs. 6. Spin-polarized total densities of states (TDOS) of orthorhombic structure. Figs. 7. Spin-polarized total densities of states (TDOS) of monoclinic structure.

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Fig. 8. Spin resolved band structure of FC5N8 monoclinic structure.

Fig. 9. The partial density of electronic states of FC5N8 monoclinic structure.

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Fig. 10. Spin resolved band structure of (a) BeC5N8 tetragonal structure.

Table captions

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Table 1. Lattice constant a(Å), bulk modulus B (in GPa), pressure derivative of bulk modulus B’ and band gaps (in eV) for C3N4.

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Table 2. Total and partial magnetic moment (in µB) for Li-, B-, Be- and F- doped C3N4.

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compounds

a

c

B

B'

Eg

Tetragonal(P-42m)

3.459

-

401.759

3.821

2.68

Defect zb- C3N4(P43m) 3.458

-

389.515

4.043

2.68

425a, 430e 434c,

3.40a

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Table. 1

Cubic -C3N4(I-43d)

5.451

-

5.3973b

438.852

3.903

496b, 480e

3.30d

477c 6.410

2.400

6.41a

2.404a

407.485

51a

223c

Ref. [36].

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f

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Ref. [31]. Ref. [8]. c Ref. [32]. d Ref. [33]. e Ref. [34]. b

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a

2.90 4.30

3.81c

3.865

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β-C3N4(P-3)

3.80c

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3.4232b

4.35c

3.47 4.85

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Table. 2

Monoclinic

LiC5N8

-

-

-

-

-

mtot

0.87

2.00

0.09

mc

-0.008

-0.018

0.002

mN

0.134

0.306

0.006

mx

-0.002

0.007

0.021

Interstitial

0.236

0.564

-

-

-

mtot

0.82

mc

-0.007

mN

0.123

mx

0.001

Interstitial

mtot

2.94

-0.028

0.455

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0.024

0.033

0.857

-

-

1.79

0.45

1.97

-0.009

0.004

-0.015

0.256

0.046

0.288

0.008

0.107

0.012

0.207

0.486

0.113

0.529

-

-

-

-

0.14

0.85

1.00

1.06

-0.001

0.002

0.001

-0.001

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mc

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FC5N8

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Orthorhombic

BeC5N8

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Tetragonal

BC5N8

0.079

0.105

0.172

0.535

mx

-0.001

-0.001

0.281

0.022

0.039

0.289

0.197

0.343

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mN

Interstitial

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T e tr a g o n a l

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T e tra g o n a l

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-6 6 6 ,1 5

D e fe c t z in c -b le n d e

C 3N 4

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 

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2 ,0

8 6

4

4 2

2 0

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1

2

3

4

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4

6

6 3

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T o ta l 0

0

-3

-3

-6

-6

-9

-9

Γ M

K

Γ

A

T o ta l D e n s itie s o f s ta te s

5

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F ig , 5

4 ,5 4

B C 5N 3

B e C 5N

3 ,0

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0 ,0

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4

-1 ,5

-3 ,0

-6

-4

-2

0

E n e rg y (e v )

2

4

6

-6

-4

-2

0

E n e rg y (e v )

2

ACCEPTED MANUSCRIPT

F ig , 8

6

4

4

SC

RI PT

6

M AN U

2

E n e rg y (e V )

2

0

TE D

0

-2

AC C

EP

-2

E

-4

-6

Γ M

K

Γ A

-4

-6

Γ M

K

Γ A

f

F ig , 9

ACCEPTED MANUSCRIPT

0 ,6

0 ,2

0 ,1

SC

0 ,2

C -s C -p x C -p y C -p z

RI PT

N -s N -p x N -p y N -p z

0 ,0

-0 ,2

EP

-0 ,1 -0 ,1 -0 ,2

-0 ,3

-0 ,4

-0 ,6

-0 ,2 -3

-2

-1

0

1

E n e rg y (e V )

2

3

0 ,4

0 ,0

TE D

0 ,0

F -s F -p x F -p y F -p z

0 ,2

M AN U

0 ,1

AC C

D e n s ity o f S ta te s ( S t/e V s p in f .u )

0 ,3

-3

-2

-1

0

E n e rg y (e V )

1

2

3

-3

-2

-1

0

E n e rg y (e V )

1

2

3

ACCEPTED MANUSCRIPT

F ig , 1 0

6

4

4

SC

RI PT

6

M AN U

2

E n e rg y (e V )

2

0

TE D

0

-2

AC C

EP

-2

E

-4

-6

W L

Γ

X W K

-4

-6

W L

Γ

X W K

f

ACCEPTED MANUSCRIPT Highlights

RI PT

(1) Based on DFT, GGA calculations, (Li, B, Be, F)C5N8 have been investigated.

(2) Some physical properties of (Li, B, Be, F)C5N8 have been investigated.

AC C

EP

TE D

M AN U

SC

(3) Detection of half-metallic state in F/Be substituted C3N4.