Adsorption and magnetic properties of Cu11MO12 (M = Cu, Ni and Co): Ab initio study

Adsorption and magnetic properties of Cu11MO12 (M = Cu, Ni and Co): Ab initio study

Results in Physics 7 (2017) 4419–4426 Contents lists available at ScienceDirect Results in Physics journal homepage: www.journals.elsevier.com/resul...

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Results in Physics 7 (2017) 4419–4426

Contents lists available at ScienceDirect

Results in Physics journal homepage: www.journals.elsevier.com/results-in-physics

Adsorption and magnetic properties of Cu11MO12 (M = Cu, Ni and Co): Ab initio study I.A. Abdel-Latif a,b,c,⇑, H.Y. Ammar a a

Physics Department, College of Science & Arts, Najran University, P.O. 1988, Najran, Saudi Arabia Advanced Materials and Nano-Research Centre, Najran University, P.O. Box: 1988, Najran 11001, Saudi Arabia c Reactor Physics Department, NRC, Atomic Energy Authority, Abou Zabaal P.O. 13759, Cairo, Egypt b

a r t i c l e

i n f o

Article history: Received 19 September 2017 Received in revised form 9 November 2017 Accepted 9 November 2017 Available online 16 November 2017

a b s t r a c t Hydrazine is toxic material that is recently used in wide scale and so we need to develop efficient sensing systems with high flexibility, and low capital cost for control recognition the adsorption of such materials. The structural stability, electronic and magnetic properties of nanocomposite of Cu11MO12 (M = Cu, Ni and Co) have been analyzed in the present work. By employing the density functional theory DFT based on ab initio approach, we studied the effect of hydrazine on the magnetic and electronic properties of Cu11MO12 (M = Cu, Ni and Co). The interaction between N2H4 molecules with the sorbent clusters is attributed to the donation – back donation mechanism. Ni and Co doping may lead to increase in electric conductivity of the CuO nanocluster. The total magnetic moments (l) showed that the magnetic moment of our clusters depends on the spin of electrons in 3d orbital and there is increase in the magnetic moment with substitution of Ni and Co. There is no change in the total magnetic moment as a result of the adsorption of hydrazine for Cu12O12 and Cu11NiO12 clusters while the change occurred only in Cu11CoO12 cluster. Ó 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Introduction Hydrazine is widely used in several chemical industries such as a foaming agent in preparing polymer foams in addition it is highly toxic compound. Thus, in order to reduce environmental pollution, it is necessary to use catalysts/sorbents to remove or trap the hydrazine. Metal oxides specially, transition metal oxides can be used for this purpose. The transition metal element in transition metal oxides plays an important role in determination of its physical and chemical properties. The 3d raw of transition metals have relatively natural abundance because of their production in nonexplosive nucleosynthesis that is gives its particular interest [1]. So a large number of theoretical and experimental studies have been done on transition metals oxides. Copper oxides have considerable industrial significance because of their catalytic behavior, at a much lower cost than other oxides. Different theoretical methods are used to study the physical and chemical properties of CuO [1]; for example Complete Active Space Self Consistent Field (CASSCF) [2], Plane Wave Pseudo Potential-Local Spin Density Approximation (PWPPLSDA) [3], Plane wave Pseudo Potential-Generalized Gradient Approximation (PWPP-GGA) [3], Configuration Interac⇑ Corresponding author at: Physics Department, College of Science & Arts, Najran University, P.O. 1988, Najran, Saudi Arabia. E-mail address: [email protected] (I.A. Abdel-Latif).

tion by Perturbation of a multi configurations wave functions Selected Iteratively (CIPSI) [4], Local Spin Density Approximation (LSDA) [5], B3LYP (Becke three parameters, Lee, Yang and Parr) [6] and PBE-GGA (Perdew functional with Generalized Gradient Approximation) [7] methods. Copper oxide has been found to be as an active component of different catalysts, especially of those promoting reactions of CO at mild temperatures. According to Chen and Wu [8] CuO/c-Al2O3 monolayer dispersed catalysts possess a higher catalytic activity at room temperature for the reduction of NO in the presence of CO or oxidation of CO. They developed a highly sensitive, low cost, simple chemical sensor. CuO. The adsorption on different types of surfaces is increasingly investigated both at a theoretical and experimental level [9]. The adsorption of nitrogen dioxide molecule (NO2) on Li atom was calculated by Eid and Ammar [10] using density functional theory (DFT) in combination with embedded cluster model and the adsorption of bromobenzene and aniline on Cu2O(1 1 0) was calculated by Man et al. [9]. Man proved that the van der Waals forces are important components of the total adsorption energies for these systems. The structural stability, electronic band structure and magnetic properties of both zigzag and armchair shapes of copper oxide nanotubes have been analyzed by Paudel [11] where they are used spin polarized generalized gradient approximation based on a standard Density Functional Theory DFT. They found that CuO nanotubes showed the highest degree of spin polarization and the total mag-

https://doi.org/10.1016/j.rinp.2017.11.011 2211-3797/Ó 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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netic moment was found to be highest for (4, 0) zigzag and (3, 3) armchair. CuO could be used for different sensors; for example in Ref. [12] they fabricated humidity and temperature sensors by utilizing copper oxide-Si-adhesive composite and pure copper oxide nano-sheets. In the present work, the structural stabilities, electronic and magnetic properties of Cu11MO12 (M = Cu, Ni and Co) were investigated using density functional theory (DFT) method in nano-scale and compared with the experimental data. As well as the adsorption properties of hydrazine molecule on Cu11MO12 were studied.

Computational methods Density functional theory (DFT) [13] methods were employed for the calculations of the adsorbate-substrate interactions. DFT calculations were performed by using Becke’s three-parameter (B3) with Lee, Yang and Parr (LYP) correlation functional [14]. This B3LYP hybrid functional includes a mixture of a Hartree-Fock exchange with DFT exchange correlation and is based on the exact form of the Vosko-Wilk-Nusair correlation potential [15] that is used to extract the local part of the LYP correlation potential. Orig-

Fig. 1. The optimized structure of Cu11MO12 and N2H4/Cu11MO12 clusters at B3LYP/LANL2dz.

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Fig. 2a. The relation between Spin and the relative change in the total energy at B3LYP/LAnL2dz.

Fig. 3. IR spectra of Cu11MO12 clusters at B3LYP/LAnL2dz.

Fig. 2b. The relation between Spin and the relative change in the total energy at ROHF/LAnL2dz.

inally the functional B included the Slater exchange along with corrections involving the gradient of the density [16] and the correlation functional LYP is that of Lee, Yang and Parr, which includes both local and non-local terms [17,18]. The gradient-corrected exchange functional methods (Perdew- Burke -Wang PBW91 and Perdew-Burke-Ernzerhof PBEPBE) are used as well [19,20]. All calculations were done using Gaussian09 suite of program [21]. Densities of states (DOS) for Cu11MO12, adsorbate and complex systems were calculated for alpha electrons using GaussSum2.2.5 program[22], Full natural bond orbital (NBO) analyses were made to calculate the charge distribution for substrates, adsorbates and complex systems by using NBO version 3.1 [23].

LanL2dz basis set was used for Cu, Ni, Co, O, N and H atoms. The core electrons of Cu, Ni and Co atoms are treated within the frozen core approximation. The pristine CuO nano-cluster was represented by a quantum cluster of 24 atoms, Cu12O12. And to study he effect of doping on CuO properties a Cu atom was replaced by TM atom (TM = Ni, Co) to form Cu11NiO12 and Cu11CoO12 nanoclusters. Fig. 1 shows the relaxed pristine and doped CuO nano-clusters. Results and discussions Cu11MO12 geometries and stabilities To obtain the most stable structure for the studied cluster, we begin our optimizations for Cu12O12, Cu11CoO12 and Cu11NiO12 clusters at B3LYP/LanL2dz level of calculations with the lowest possible spin states, S = 0, 0 and 1/2, respectively. Then the opti-

Table 1 The Bond length (Å), binding energies (eV), dipole moment (Debye), HOMO (eV), LUMO (eV) and NBO atomic charge (|e|) of Cu11MO12 Clusters. Structure

dM-O14 dM-O15 dM-O23 Eb D a HOMO a LUMO b HOMO b LUMO QM

Cu12O12

Cu11NiO12

Cu11CoO12

B3LYP

BPW91

pbepbe

B3LYP

BPW91

pbepbe

B3LYP

BPW91

pbepbe

1.98 1.94 1.90 2.78 0.05 7.76 2.81 7.06 5.17 1.03

1.96 1.98 1.91 3.07 0.007 6.38 3.55 6.17 5.86 0.92

1.95 1.98 1.91 3.25 0.005 6.39 3.62 6.19 5.89 0.92

1.95 1.93 1.89 2.84 0.98 7.58 2.77 6.90 5.26 1.08

1.93 1.91 1.85 3.14 1.04 6.28 3.48 6.05 5.84 0.93

1.93 1.91 1.85 3.32 1.03 6.29 3.56 6.07 5.87 0.94

1.84 1.83 1.84 2.82 0.88 7.40 5.40 6.85 5.31 1.13

1.83 1.86 1.82 3.15 0.57 6.20 5.76 6.10 5.84 0.95

1.84 1.84 1.81 3.35 1.33 6.12 5.78 6.05 5.82 0.98

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Table 2 The adsorption parameters of N2H4/Cu11MO12 clusters. Structure

dM-O14 (Å) dM-O15 (Å) dM-O23 (Å) dN-N (Å) dN25-H26 (Å) dN25-H27 (Å) dN28-H29 (Å) dN28-H30 (Å) dN25-M (Å) D (Debye) Eads. a HOMO a LUMO b HOMO b LUMO

N2H4/Cu12O12

N2H4/Cu11NiO12

N2H4/Cu11CoO12

B3LYP

BPW91

pbepbe

B3LYP

BPW91

pbepbe

B3LYP

BPW91

pbepbe

1.93 2.08 1.99 1.46 1.03 1.02 1.03 1.03 2.09 9.26 1.83 6.99 2.22 6.51 4.66

1.95 2.07 2.00 1.47 1.04 1.03 1.03 1.03 2.11 9.67 1.65 5.61 2.91 5.64 5.32

1.95 2.07 2.00 1.47 1.04 1.03 1.03 1.04 2.10 5.67 1.88 5.61 3.00 5.66 5.35

2.01 1.98 1.94 1.47 1.03 1.02 1.02 1.02 2.16 10.88 1.78 6.81 2.23 6.43 4.70

1.95 1.98 1.93 1.47 1.04 1.03 1.03 1.03 2.15 10.95 1.59 5.51 2.90 5.60 5.38

1.94 1.98 1.93 1.47 1.04 1.03 1.03 1.03 2.15 10.87 1.82 5.51 2.98 5.62 5.41

1.92 1.96 1.91 1.47 1.03 1.03 1.03 1.02 2.02 9.41 1.38 6.80 2.35 6.42 4.67

1.82 1.88 1.81 1.46 1.04 1.03 1.03 1.03 2.00 5.70 1.86 5.79 4.33 5.82 5.56

1.82 1.88 1.81 1.46 1.05 1.03 1.03 1.03 2.00 9.62 2.12 5.79 4.35 5.84 5.60

Table 3 The NBO atomic charges for free hydrazine and N2H4/Cu11MO12 clusters. NBO charges

QM QN25 QH26 QH27 QN28 QH29 QH30 QN2H4

Free N2H4

N2H4/Cu12O12

N2H4/Cu11NiO12

BPW91

pbepbe

B3LYP

BPW91

pbepbe

B3LYP

BPW91

pbepbe

B3LYP

BPW91

pbepbe

– 0.74 0.36 0.38 0.74 0.36 0.38 0.00

– 0.74 0.36 0.38 0.74 0.35 0.38 0.00

– 0.74 0.36 0.38 0.74 0.36 0.38 0.00

0.97 0.72 0.45 0.41 0.72 0.45 0.42 0.29

0.86 0.72 0.45 0.42 0.72 0.45 0.42 0.31

0.85 0.72 0.45 0.42 0.72 0.45 0.42 0.31

1.04 0.73 0.45 0.41 0.72 0.44 0.42 0.27

0.87 0.72 0.45 0.41 0.72 0.44 0.42 0.29

0.86 0.72 0.45 0.42 0.72 0.45 0.42 0.30

0.818 0.67 0.45 0.44 0.68 0.42 0.39 0.35

0.75 0.64 0.46 0.45 0.65 0.41 0.39 0.43

0.74 0.64 0.46 0.45 0.65 0.42 0.42 0.44

mization process was repeated at the higher spin states gradually. Fig. 2a shows the relative change in the total cluster energy (DE) versus its spin state. The (DE) is calculated by using the following

DE ¼ Es  Esmin

ð1Þ

where, Es and Esmin are the total energies of the cluster at spin state (s) and at its lowest spin state, respectively. Furthermore, spin-restricted open-shell ROHF calculations were carried out to examine the effect of spin contamination [24], see Fig. 2b. We found the most stable structures for Cu12O12, Cu11CoO12 and Cu11NiO12 clusters at 12/2, 12/2 and 13/2 spin states, respectively. The bond lengths dM-O (M = Cu, Ni and Co), dipole moment, HOMO and LUMO energy levels are listed in Table 1. Our calculated CuAO bond length are in the range of 1.88–1.98 Å in good agreement with those reported by Khan et al. [25]. The average binding energies per atom (Eb ) have been calculated by using Eq. (1)

Eb ¼

N2H4/Cu11CoO12

B3LYP

1 ðECu11 MO12  ð11Ecu þ EM þ 12EO ÞÞ 24

ð2Þ

where, ECu11 MO12 , Ecu ; EM and EO is the total energy of the cluster, the energy of single Cu, M and O atom, respectively. According to Eq. (2), as the stability of the cluster increases as the negativity of Eb increases. The binding energy values for Cu12O12, Cu11CoO12 and Cu11NiO12 clusters are 2.78, 2.82 and 2.84 eV, respectively i.e., the presence of dopant atom slightly increases the cluster stability. The IR calculations have been performed for the studied clusters (see Fig. 3). From calculated IR

spectra, no negative frequencies were obtained, and this confirms the stability of the cluster. N2H4 adsorption on Cu11MO12 clusters To examine the adsorption of N2H4 molecule on the Cu11MO12 clusters, a geometrical optimization was performed for the free N2H4 molecule, the adsorbent Cu11MO12 clusters and N2H4 /Cu11MO12 complexes. Then the adsorption energies (Eads: ) given by:

Eads: ¼ EN2 H4 =Cu11 MO12  ðECu11 MO12 þ EN2 H4 Þ

ð3Þ

where, EN2 H4 ; ECu11 MO12 and EN2 H4 =Cu11 MO12 are the total optimized energies of the free N2H4 molecule, Cu11MO12 cluster and N2H4/Cu11MO12 complexes, respectively. It is known that the hydrazine molecule has three major conformations [26,27] in the gas phase; gauche, trans and eclipsed. Gauche structure was considered because it is the most stable structure of N2H4 and it can interact with the sorbent clusters with different orientations to form different conformations of the N2H4/ Cu11MO12 complexes. The most stable N2H4/Cu11MO12 complexes that considered in our calculations are shown in Fig. 1. The adsorption properties of N2H4 are listed in Table 2. One can see that, the interactions between N2H4 molecule with the three adsorbent Cu11MO12 clusters, are exothermic interactions and bonds are formed between N2H4 molecule and Cu11MO12 clusters. According to B3LYP calculations, the adsorption energies (Eads) of N2H4 on the sorbent clusters are 1.83,1.78, and 1.38 eV for N2H4 /Cu12O12, N2H4 /Cu11NiO12 and N2H4 /Cu11CoO12, respectively. Values of adsorption energy resulted from BPW91 calculations are 1.65, 1.59, and 1.86 eV and from PBEPBE calculations are

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Scheme 1. HOMO and LUMO surfaces of hydrazine and CuO nanocluster showing the electrophilic characters of Cu atoms and nucleophilic character of O atoms which explain the donation back donation mechanism.

1.88, 1.82, and 2.12 eV for N2H4/Cu12O12, N2H4/Cu11NiO12 and N2H4/Cu11CoO12, respectively. One can notice that, in all cases the reaction between hydrazine molecule and the sorbent cluster is exothermic reaction. The bond lengths between the two nitrogen atoms (dN-N) in the N2H4/Cu11MO12 complexes are longer than those of the free N2H4 molecules (1.41 Å). The dipole moment values of N2H4/Cu11MO12 complexes (see Table 2) are higher than the dipole moment values of the corresponding sorbent Cu11MO12 clusters (see Table 1). These results can be illustrated in terms of the following factors: a) Charge transfer: Hydrazine molecule can be viewed as a combination of two NH2 fragments. Each of NH2 group has a lone-pair on its N atom. Thus, hydrazine adsorption on metal surface could serve as model for the molecular adsorption that involves lone-pair interaction [27]. And one can expect an electron donation from the N lone pair to the empty d orbitals of the transition metal. This may lead to the decrease of the negative charges on nitrogen atoms in contrast with our results shown in Table 3. The interpretation of this contrast could be illustrated as follow: i) According to B3LYP calculations, when the total positive charges increased on N2H4 in N2H4 /Cu11MO12 complexes an unexpected decrease in the adsorpitivity observed.

ii) The negative charges on nitrogen atoms, calculated using both BPW91 and PBEPBE methods, approximately have no change in N2H4/Cu12O12 and N2H4/Cu11NiO12 complexes. The positive charges on hydrogen atoms increased from the range 0.35 to 0.38|e| for the free molecule to be in the range of 0.42–0.45|e| for the hydrogen atom in N2H4/Cu11MO12 complexes. These changes in charge in our complexes (N2H4/Cu11MO12) increase the polarizability and this polarization may lead to an increase in dipole moment. That is why we suggest that the interaction between N2H4 molecules with the sorbent clusters is a donation –back donation mechanism. Scheme 1 illustrates the mechanism of donation – back donation of electrons between N2H4 and Cu11MO12. a) HOMO and LUMO energy levels; it is known that one of the most important factors in HOMO and LUMO interactions is the energy difference between HOMO of the electron donor and LUMO of the electron acceptor. The chemical bonding of hydrazine molecule in N2H4/Cu11MO12 complexes could be attributed to electron donation from the HOMO of N2H4 to the empty LUMO orbitals of the sorbent. The HOMO and LUMO Energy levels of hydrazine molecule and sorbent clusters are depicted in Fig. 4. It is clear that, the energy difference between HOMO of hydrazine (electron donor) and the nearest LUMO of Cu12O12, Cu11NiO12 and Cu11CoO12 clusters

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Electronic and magnetic properties

Fig. 4. The HOMO and LUMO energy levels of hydrazine molecule and the sorbent Cu11MO12 clusters at B3LYP/LAnL2dz.

(electron acceptors) at B3LYP calculations are 0.05, 0.14 and 0.19 eV, respectively. This values explain the trend of the Eads for N2H4/Cu12O12 > N2H4/Cu11NiO12 > N2H4/Cu11CoO12.

NPA analysis Natural population analysis (NPA) is carried out in order to understand the interaction between Cu, Ni, Co and O in CuO. The valence configurations and charge of Cu, Ni, Co and O atoms are listed in Supplementary Table 1. The valence configurations of Cu1 atom in Cu12O12, Cu11NiO12 and Cu11CoO12 are ([core] 4S0.283d9.434p0.29), ([core] 4S0.26 3d9.44 4p0.28) and ([core] 4S0.283d9.464p 0.28) respectively. From this configuration it is quite clear that 4 s and 4p shells have no role in electric and magnetic properties and mainly 3d shell is responsible for electronic and magnetic properties. The configuration of Oxygen; for example O12 in our 3 cases without hydrazine are [core] 2S1.842p5.17, [core] 2S1.84 2p5.18 and [core]2S1.842p5.17 (almost the same) where porbital is responsible for its properties. The charge transfer occurs mainly from 3d in Cu, Ni and Co to 2p in Oxygen resulting in hybridization between the 2p and 3d orbitals. Apparently, the 3d shell of Cu in Cu12O12 has no change and this behavior is similar to those reported in [28–30]. The valence configurations of Cu24, Ni24 and Co24 atoms in Cu11MO12 clusters are ([core] 4S0.253d9.444p0.28), ([core] 4S0.25 3d8.39 4p0.28) and ([core] 4S0.243d7.324p0.304d0.01) respectively. For more details about electronic configuration and NBO charges see Suppl. Table 1. From this configurations it is quite clear that any change in electric and magnetic properties among Cu11MO12 clusters may attributed to the dopant atom. As it is well known that CuO is a class of antiferromagnetic materials but the weak ferromagnetic order was reported by Punnoose et al. [31] and Zheng et al. [32] where the uncompensated surface spins produce a ferromagnetic/antiferromagnetic (FM/AF) interface in the pure antiferromagnetic nanoparticles (AFN) [33]. We calculate the difference in total magnetic moment (l) of the clusters due to the adsorption of hydrazine as the following equation.

Dl ¼ lðN 2 H4 =Cu11 MO12 Þ  lðCu11 MO12 Þ

ð4Þ

where lðN 2 H4 =Cu11 MO12 Þ is the total magnetic moment of the N2H4/Cu11MO12 complexes and lðCu11 MO12 Þ is the total magnetic

Table 4 The local magnetic moment of 4 s, 3d, 4p and 5p spin states for M atoms in Cu11MO12 clusters using BPW91/LanL2dz. Compound

4S

Cu12O12 N2H4/Cu12O12 Cu11NiO12 N2H4/Cu11NiO12 Cu11CoO12 N2H4/Cu11CoO12

3d

4p

Total

Q (e)

l (lB)

Q (e)

l (lB)

Q (e)

l (lB)

0.28 0.30 0.26 0.27 0.27 0.29

0.01 0.02 0.00 0.01 0.01 0.01

9.49 9.47 8.51 8.50 7.45 7.53

0.44 0.46 1.41 1.43 2.36 1.66

0.30 0.37 0.30 0.36 0.33 0.43

0.02 0.01 0.00 0.01 0.01 0.02

0.41 0.43 1.41 1.41 2.34 1.64

Table 5 The local magnetic moment of 4s, 3d, 4p and 5p spin states and total magnetic moment for Cu11MO12 clusters. Compound

l (lB) 4S

Cu12O12 N2H4/Cu12O12 Cu11NiO12 N2H4/Cu11NiO12 Cu11CoO12 N2H4/Cu11CoO12

3d

4p

5p

Total

B3LYP

BPW91

B3LYP

BPW91

B3LYP

BPW91

B3LYP

BPW91

B3LYP

BPW91

0.18 0.19 0.15 0.14 0.13 0.07

0.10 0.1 0.08 0.05 0.11 0.03

6.12 6.20 7.20 7.22 7.23 7.07

5.10 5.07 6.04 6.01 6.38 5.93

0.16 0.11 0.14 0.10 0.09 0.17

0.02 0.14 0.06 0.11 0.12 0.09

0.06 0.11 0.04 0.07 0.07 0.53

0.16 0.03 0.08 0.03 0.01 0.08

5.72 5.79 6.87 6.58 6.94 6.30

4.82 4.80 5.82 5.82 6.14 5.73

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shown. Also the HOMO and LUMO energy levels for spin up (a) and down (b) are calculated and listed in Table 1 for Cu11MO12 clusters and in Table 2 for N2H4/Cu11MO12 clusters. From Fig. 5, it is shown that the Cu12O12, Cu11NiO12 and Cu11CoO12 clusters are semiconductor materials with HOMO-LUMO gaps of 1.89, 1.65 and 1.45 eV, at B3LYP calculations, respectively. The experimental energy gap of 1.8 and 2.4 were reported for bulk and nanoparticles CuO by Radhakrishnan and Beena [34] which are in good accordance with our results calculated from B3LYP. It is clear that the Ni and Co doping atoms shifted the HOMO and LUMO energy levels and decreases the HOMO-LUMO gaps of the cluster. It is well known that the HOMO-LUMO gaps (Eg) is a major factor determining the electrical conductivity of a material and a classical relation between them is as follows [35]:

  Eg 2kT

r a exp

ð5Þ

where, r is the electrical conductivity and k is the Boltzmann’s constant. It is clear that the Ni and Co doping increases the electric conductivity of the cluster. The adsorption of N2H4 on Cu11MO12 changes the HOMO-LUMO gaps by the ratio 2.11%, +4.80% and +27.5% for Cu12O12, Cu11NiO12 and Cu11CoO12, respectively. Therefore, the Co doping atom increases the sensitivity of CuO toward N2H4 molecule. Conclusions

Fig. 5. The DOS of Cu11MO12 and N2H4/Cu11MO12 clusters at B3LYP/LAnL2dz.

moment of the Cu11MO12 clusters. Local magnetic moment and charge of 4s, 3d, and 4p states for M atoms in Cu11MO12 and N2H4/Cu11MO12 clusters were calculated using BPW91 method and listed in Table 4. It is clear that, the N2H4 adsorption make no change in local magnetic moment of M atom in Cu12O12 and Cu11NiO12 clusters, while it makes a change of 0.7 lB for Co atom in Cu11CoO12 cluster. The magnetic moment of 4s, 3d, 4p and 5p states of transition metal atoms in Cu11MO12 and total magnetic moments (lB), using B3LYP and PBW91 methods, are listed in Table 5. Moreover, spin of all transition metals atoms in under-investigation clusters are listed in Suppl. Table 2. It is found that the magnetic moment depends on the spin of electrons in 3d orbital and there is increase in the resultant magnetic moments from 4.82lB in Cu12O12 with substitution of Ni and Co to 5.82 and 6.14 lB, respectively. One can note that the change in local magnetic moments between M atom in Cu12O12 and Cu11NiO12 clusters (from Table 4) is the same change in the total magnetic moments of the two clusters (from Table 5) which is 1.0 lB. One can conclude that the doping of Ni atom in the cluster does not affect the total magnetic moment of the rest Cu atoms in the cluster. On the other hand, there is no change in the total spin for Cu12O12 and Cu11NiO12 as a result of N2H4 adsorption. According to Table 4, the difference in local magnetic moment of M atoms in Cu12O12 and Cu11CoO12 clusters is 1.93 lB and from Table 5 the difference in total magnetic moment is 1.32 lB. This means that there is change in spin of the other cu atoms in the complex. Besides, there is change in the magnetic moment for Cu11CoO12 as a result of N2H4 adsorption. DOS analysis Density of states (DOS) analysis were carried out to study the influence of dopant and hydrazine adsorption on the electronic properties of the Cu12O12 clusters. In Fig. 5 the total DOS of the considered structures are plotted where spin up (a) and down (b) are

As a result of Ni and Co doping, the electric conductivity of the CuO cluster increased. The donation-back donation mechanism is found to describe the interaction between N2H4 molecules with the sorbent clusters. The HOMO-LUMO gaps is changed due to the adsorption of N2H4 on Cu11MO12 by the ratio 2.11%, +4.80% and +27.5% for Cu12O12, Cu11NiO12 and Cu11CoO12, respectively so we can say that the Co doping atom increases the sensitivity of CuO toward N2H4 molecule. There is no change in the total magnetic moment as a result of the adsorption of hydrazine for Cu12O12 and Cu11NiO12 clusters while the change occurred only in Cu11CoO12 cluster. Acknowledgment The author is thankful to the Deanship of Scientific Research for Grant Research code NU/ESCI/14/019 to Dr. I. A. Abdel-Latif, Najran University, Saudi Arabia. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at https://doi.org/10.1016/j.rinp.2017.11.011. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]

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