BIBECHANA 18 (2) (2021) 68-79 68 Electronic and magnetic properties of defected MoS2 monolayer Hari Krishna Neupane1, 2, Narayan Prasad Adhikari2* 1Amrit Campus, Institute of Science and Technology Tribhuvan University, Kathmandu, Nepal 2Central Department of Physics, Institute of Science and Technology Tribhuvan University, Kathmandu, Nepal *Email: narayan.adhikari@cdp.tu.edu.np Article Information: Received: December 28, 2020 Accepted: April 17, 2021 Keywords: DFT Magnetic moment Monolayer Spins Vacancy defects ABSTRACT It is interesting to understand the effect of defects in 2D materials, because vacancy defects in 2D materials have novel electronic and magnetic properties. In this work, we studied electronic and magnetic properties of 1S vacancy defect (1Sv-MoS2), 2S vacancy defects (2Sv-MoS2), 1Mo vacancy defect (Mov-MoS2), and (1Mo & 1S) vacancy defects ((Mo-S)v-MoS2) in 2D MoS2 material by first- principles calculations within spin-polarized density functional theory (DFT) method. To understand the electronic properties of materials, we have analyzed band structures and DOS calculations, and found that 1Sv-MoS2 & 2Sv-MoS2 materials have semiconducting nature. This is because, 1Sv-MoS2 & 2Sv-MoS2 materials open small energy band gap of values 0.68 eV & 0.54 eV respectively in band structures. But, in Mov-MoS2 & (Mo-S)v-MoS2 materials, energy bands around the Fermi level mix with the orbital’s of Mo and S atoms. As a result, bands are split and raised around and above the Fermi energy level. Therefore, Mov-MoS2& (Mo-S)v-MoS2 materials have metallic nature. We found that MoS2, 1Sv-MoS2& 2Sv-MoS2 materials have non-magnetic properties, and Mov-MoS2& (Mo-S)v-MoS2 materials have magnetic properties because magnetic moment of MoS2, 1Sv-MoS2& 2Sv-MoS2 materials have 0.00 µB/cell value and Mov-MoS2& (Mo-S)v-MoS2 materials have 2.72 µB/cell & 0.99 µB/cell respectively. Therefore, non-magnetic MoS2 changes to magnetic Mov-MoS2 & (Mo-S)v-MoS2 materials due to Mo and (1Mo & 1S) vacancy defects. Magnetic moment obtained in Mov- MoS2& (Mo-S)v-MoS2 materials due to the distribution of up and down spins in 4p, 4d & 5s orbitals of Mo atoms and 3s & 3p orbitals of S atoms in structures. The significant values of magnetic moment are given by distributed spins in 4d orbital of Mo atoms and 3p orbital of S atoms. DOI: https://doi.org/10.3126/bibechana.v18i2.33905 This work is licensed under the Creative Commons CC BY-NC License. https://creativecommons.org/licenses/by-nc/4.0/ mailto:narayan.adhikari@cdp.tu.edu.np https://doi.org/10.3126/bibechana.v18i2.33905 https://creativecommons.org/licenses/by-nc/4.0/ http://nepjol.info/index.php/BIBECHANA Hari Krishna Neupane and Narayan Prasad Adhikari / BIBECHANA 18 (2) (2021) 68-79 69 1. Introduction Two dimensional (2D) materials with atomic thickness have become candidates for wearable electronic devices in the future. Graphene and transition metal sulfides have received extensive attention in logic computing and sensing applications due to their lower power dissipation [1-3]. However, the lack of intrinsic band gap and non-magnetic nature of graphene limits its practical applications in widely expanding field of carbon- based devices. Therefore, the transition metal dichalcogenides material (TMD) Molybdenum diSulphide (MoS2) is a suitable candidate for logic computing (logic computing is the sequence of operations (hardware or software) performed by computers) and sensing (devices) applications. MoS2 is made by Mo and S atoms stacked together to give S-Mo-S in a triangular prismatic arrangement [4]. The band structure of MoS2 depends on the number of layers, and the single layer MoS2 has a direct band gap of energy 1.80 eV [5]. The band is opened in between the lower energy band of conduction band and higher energy band of valence band. Due to the wide band gap (1.80 eV), MoS2 provides huge opportunities for electrical and optoelectronics [6-9]. In recent years, a lot of research has been carried out surrounding MoS2, and various new electronic devices based on MoS2 have emerged, including gas sensors, resistive memory, photo detectors, integrated logic circuits, signal amplifiers, flexible optoelectronic devices, solar cells and lubricants etc. [10-13]. Electronic and magnetic properties of 2D pristine and defected materials are attracting properties in solid-state physics because they have potential applications in industrial as well as academic sectors. Hence, it is interesting to understand the effect of defects in 2D materials [14-16]. The vacancy defects in solids causes deviation of atoms or ions from the periodicity and they are used to find innovative properties. They can be used to design new materials [17]. To our best knowledge, Mo and S atoms vacancy defects (i.e. 1Mo atom only, 1Mo and 1S atoms together) in monolayer MoS2 material have not been reported [5, 18-21]. These Mo and S atoms vacancy defects in MoS2 may provide significance outline for the material in device applications. Therefore, in this work, we focus on the electronic and magnetic properties of Mo and S atoms vacancy defects in monolayer MoS2 through first-principles calculations within the frame work of density functional theory (DFT), using computational tool quantum ESPRESSO. The remaining part of this paper is arranged as follows. In section 2, we introduce the computational details. Main finding and their interpretation are presented in section 3. Finally we draw conclusions in section 4. 2. Computational Methods In this work, we used spin-polarized density functional theory (DFT) [22], with the quantum ESPRESSO simulation package [23] and structure visualization program XCrySDen [24], to perform all the calculations. The Generalized Gradient Approximation (GGA) of Perdew-Burke-Ernzerhof (PBE) [25] is used to describe the exchange correlation interactions. The Rappe-Rabe-Kaxiraas- Joannopoulos (RRKJ) model of ultra-soft pseudo- potentials is used to describe chemically active valence electrons in calculations. The kinetic energy cut-off and charge density cut-off values are set to 35 Ry and 350 Ry respectively for the plane- wave expansion. The first Brillouin zone is sampling of a (10×10×1) Monkhorst-Pack (MP) [26] k-points grid, which is used to perform geometric optimizations. All the structures are fully relaxed by Broyden-Fletcher-Goldfarb-Shanno (BFGS) scheme [27], until the energy and force are converged less than 10-4 Ry and 10-3 Ry/Bohr values respectively. The mesh of (6×6×1) k-points grid is used to perform all bands structure calculations and automatic denser mesh (12×12×1) k-points is used for density of states (DoS) and partial density of states (PDoS) calculations, where in both the cases, 100 k-points are chosen along the high symmetric points connecting the reciprocal space. The Marzarri-Vanderbilt (MV) [28] Hari Krishna Neupane and Narayan Prasad Adhikari / BIBECHANA 18 (2) (2021) 68-79 70 smearing of small width 0.001 Ry is used. In addition, we have chosen ‘david’ diagonalization method with ‘plain’ mixing mode and mixing factor of 0.6 for self consistency. In present work, we have constructed (3×3) supercell structure of monolayer MoS2 from the unit cell by extending along x and y direction as shown in figure 1(a). Then, we have generated stable and relaxed structures of 1S vacancy defect in MoS2 (1Sv-MoS2), 2S vacancy defects in MoS2 (2Sv-MoS2), 1Mo vacancy defect in MoS2 (Mov- MoS2) and (1Mo & 1S) vacancy defects in MoS2 (Mo-S)v-MoS2 materials as shown in figures 1(b-i). These prepared structures are used for further investigations. 3. Results and Discussion In this section, we reported first-principles calculations within the frame work of spin- polarized DFT method to study electronic and magnetic properties of Mo and S atoms vacancy defects in MoS2 material. 3.1 Electronic Properties The electronic properties of 1Sv-MoS2, 2Sv-MoS2, Mov-MoS2 and (Mo-S)v-MoS2materials are studied by the analysis of band structures and DoS calculations using DFT method. The optimized and relaxed structures of MoS2, 1Sv-MoS2, 2Sv-MoS2, Mov-MoS2 and (Mo-S)v-MoS2 materials are shown in figures 1(a-i) respectively. Before study the band structures and DoS calculations of 1Sv-MoS2, 2Sv- MoS2, Mov-MoS2 and (Mo-S)v-MoS2 materials, we need to understand the electronic properties of pure MoS2 material. We know that the electronic configurations of valence electrons in Mo and S atoms are [Kr] 4d5 5s1 and [Ne] 3s2 3p4 respectively. A hexagonal unit cell of monolayer MoS2 on the basis of three (1Mo & 2S) atoms in honeycomb lattice structure is initially constructed by using reported value [29, 30]. It is built up by single layers of S-Mo-S atoms. It consists of two planes of Sulphur (S) atoms and an intercalated plane of Molybdenum (Mo) atom which bounds with the Sulphur atoms in a trigonal prismatic arrangement. Each Mo atom is surrounded by six first nearest neighboring S atoms. Based on convergence test, we obtained the lattice constant ‘a’ for MoS2 equals to 3.137Å, which agrees with the reported value 3.19Å [31]. The (3×3) supercell structure of monolayer MoS2 is constructed by using the lattice constant which is three times that of the unit cell as shown in figure 1(a). We have done band structure calculations of MoS2 supercell structure, and obtained band gap energy value 1.23 eV, this value is close to reported value 1.80 eV [26]. Therefore, we also concluded that monolayer MoS2 is a wide band gap semiconductor. The band structure of monolayer MoS2 is shown in figure 2(a), where x-axis represents high symmetric points in the first Brillouin zone and y-axis represents the corresponding energy values. In addition, we have prepared stable and relaxed structures of 1Sv-MoS2, 2Sv-MoS2, Mov-MoS2 and (Mo-S)v-MoS2 by removing 1S, 2S, 1Mo and (1Mo & 1S) atoms in supercell structure of MoS2, with defects formation energy 0.52 eV, 0.76 eV, 0.64 eV and 0.87 eV respectively. These defects formation energy are calculated by using the standard formalism [32]; Ed = ET-d – (ET-p+ ndµd) … (1) where, ET-d is a total energy of a supercell with the defects, nd, is the numbers of atom removed from the perfect super cell to introduce a vacancy, µd is chemical potentials of defected atom in structures, ET-p is the total energy of the neutral perfect supercell respectively. Defects formation energy values of these materials are given in table 1. The stability of these structures is observed by binding energy calculations. Higher the value of binding energy means, systems are more stable. The binding energy of materials depends upon calculated total energy of the systems, which are also given in table 1. Hari Krishna Neupane and Narayan Prasad Adhikari / BIBECHANA 18 (2) (2021) 68-79 71 Fig. 1: (a) (3×3) supercell structure of monolayer MoS2 (b) Before 1S vacancy defect in (3×3) supercell structure of monolayer MoS2 (c) 1S vacancy defect in (3×3) supercell structure of monolayer MoS2 (d) before 2S vacancy defects in (3×3) supercell structure of monolayer MoS2 (e) 2S vacancy defects in (3×3) supercell structure of monolayer MoS2 (f) Before 1Mo vacancy defect in (3×3) supercell structure of monolayer MoS2 (g) 1Mo vacancy defect in (3×3) supercell structure of monolayer MoS2 (h) Before 1Mo & 1S vacancy defects in (3×3) supercell structure of monolayer MoS2 (i) 1Mo & 1S vacancy defects in (3×3) supercell structure of monolayer MoS2. We calculated the inter-atomic distances of atoms in pristine and defected MoS2 monolayer. It is found that compactness of the materials is decreased due to vacancy defects in structure. This is because, inter-atomic bondings are broken due to vacancy defect atom (atoms) in structures, and remaining atoms are loosely bounded to each other. The inter–atomic distances in pristine and vacancy defected MoS2 materials are given in table 2. Hari Krishna Neupane and Narayan Prasad Adhikari / BIBECHANA 18 (2) (2021) 68-79 72 Table 1: Fermi energy (Ef), Fermi energy shift (Es), bandgap energy (Eg), total energy of system (Et), defects formation energy (Ed), total value of magnetic moment (M), and magnetic moment due to total up & down spins states of electrons (µ) in 4p, 4d & 5s orbitals of Mo atoms; 3s & 3p orbitals of S atoms in 1Sv-MoS2, 2Sv-MoS2, Mov-MoS2, and (Mo-S)v-MoS2materials. Data of band structures, DoS and PDoS calculations of MoS2, Sv-MoS2, Mov-MoS2& (Mo- S)v-MoS2materials MoS2 1Sv-MoS2 2Sv-MoS2 Mov-MoS2 (Mo-S)v-MoS2 Ef (eV) -1.89 -1.97 -2.02 -2.30 -2.33 Es (eV) - 0.08 0.13 0.41 0.44 Eg (eV) 1.23 0.68 0.54 - - Et (Ry) -1741.61 -1718.60 -1696.58 -1593.42 -1570.53 Ed (eV) --- 0.52 0.76 0.64 0.87 µ due to 4p of Mo atoms (µB/cell) 0.00 0.00 0.00 0.03 0.01 µ due to 4d of Mo atoms (µB/cell) 0.00 0.00 0.00 0.73 0.23 µ due to 5s of Mo atoms (µB/cell) 0.00 0.00 0.00 0.03 0.01 µ due to 3s of S atoms (µB/cell) 0.00 0.00 0.00 0.04 0.02 µ due to 3p of S atoms (µB/cell) 0.00 0.00 0.00 1.89 0.72 T Total value of magnetic moment M (µB/cell) 0.00 0.00 0.00 2.72 0.99 Table 2: Inter-atomic distances in pristine MoS2 and vacancy defects MoS2materials, where S-S, Mo-Mo and Mo-S represent inter-atomic bonding in between any two neighbouring Sulphur atoms, any two Molybdenum atoms and nearest neighbour 1Mo and 1S atoms in structures. Inter-atomic distances of pristine MoS2 and defected MoS2 monolayer along x, y and z axis x-axis (Å) y-axis (Å) z-axis (Å) S–S Mo-Mo Mo-S S-S Mo-Mo Mo-S S-S Mo-Mo Mo-S Pristine MoS2 0.00 1.57 1.52 0.00 2.74 0.90 3.13 0.00 1.56 1S defect MoS2 0.00 1.57 1.54 0.00 2.74 0.91 3.14 0.00 1.57 2S defects MoS2 0.00 1.58 1.56 0.00 2.75 0.92 3.15 0.00 1.58 1Mo defect MoS2 0.00 1.61 1.58 0.00 2.78 0.95 3.15 0.03 1.60 1Mo & 1S defects MoS2 0.02 1.62 1.59 0.02 2.78 0.97 0.01 0.03 0.62 Hari Krishna Neupane and Narayan Prasad Adhikari / BIBECHANA 18 (2) (2021) 68-79 73 We have done band structures calculations of 1Sv- MoS2, 2Sv-MoS2, Mov-MoS2 and (Mo-S)v-MoS2 materials as shown in figures 2(b-e) respectively, where 100 k-points are taken along the specific direction of irreducible Brillouin zone by choosing Γ-M-K-Γ high symmetric points. Also, high symmetric points in the first Brillouin zone are taken along x-axis and corresponding energies are taken along y-axis. The 1Sv-MoS2 and 2Sv-MoS2 materials have opened narrow band gap of values 0.68 eV and 0.54 eV respectively as shown in figures 2(b-c). Hence, the materials resemble with the nature of semiconductors. The band gap energy value of defected materials decreases with increase in defects concentrations in MoS2 structure, which determines the conductivity strength of materials. Thus, the strength of conductivity in 2Sv-MoS2 is greater than 1Sv-MoS2. Also, conductivity of defected materials is higher than non-defected monolayer MoS2 supercell structure. On the other hand, bands states of Mov-MoS2 and (Mo-S)v-MoS2 materials split and cross the Fermi energy level as shown in figures 2(d-e) respectively. Bands around Fermi level mix with the orbital’s of Mo vacancy in Mov-MoS2, and (1Mo & 1S) vacancies in (Mo-S)v- MoS2. The states associated with the dangling bond and reconstructed Mo-S bond of vacancy occurs near the top of valence band and in conduction band, and appear as flat bands as shown in figures 2(d) and 2(e). Therefore, from the band calculations, Mov-MoS2 and (Mo-S)v-MoS2 materials have metallic nature. The vacancies position of S and Mo atoms in structures creates unpaired spins of electrons in sub-orbitals of Mo-S atoms in structures. We have calculated the Fermi energy of 1Sv-MoS2, 2Sv-MoS2, Mov-MoS2 and (Mo-S)v- MoS2 materials and found -1.97 eV, -2.02 eV, -2.30 eV and -2.33 eV values respectively. These obtained different values of Fermi energy are, due to unpaired total up & down spins states of electrons and movement of charges carriers in structures. We have analyzed DoS and PDoS calculations for the investigation of magnetic properties in materials. Figures 3(a) and 3(b) represent DoS and PDoS plots of pure monolayer MoS2; figures 4(a) and 4(b) represent total DoS plots of Sv-MoS2 and 2Sv-MoS2 materials, figures 4(c) and 4(d) represent total PDoS plots of 1Sv-MoS2 and 2Sv-MoS2 materials, figures 5(a) and 5(b) represent total DoS plots of Mov-MoS2 and (Mo-S)v-MoS2 materials, and figures 5(c) and 5(d) represent total PDoS plots of Mov-MoS2 and (Mo-S)v-MoS2 materials respectively, where the states above the horizontal line represents up spin states of electrons and a state below the horizontal line represents down spin states of electrons. 3.2 Magnetic Properties The induced magnetization in the materials is obtained by analysis of DoS and PDoS calculations of materials. The asymmetrically distributed up and down spins states of electrons in DoS and PDoS plots reflect, materials have magnetic properties, and symmetrically distributed up and down spins states of electrons in DoS and PDoS plots means, materials carry non-magnetic properties. Up and down spins states of electrons in the orbitals of Mo & S atoms are symmetrically distributed in DoS and PDoS plots of MoS2, 1Sv-MoS2 and 2Sv-MoS2 materials are shown in figures 3(a) & 3(b), figures 4(a) & 4(c), and 4(b) & 4(d) respectively. Magnetic moment due to up and down spins states of electrons in 4p, 4d & 5s orbitals of Mo atoms and 3s & 3p orbitals of S atoms in MoS2, 1Sv-MoS2 and 2Sv-MoS2 have value 0.00 µB/cell, which are given in table 1. Therefore, MoS2, 1Sv-MoS2 and 2Sv- MoS2 materials have non-magnetic properties. We have investigated magnetic properties of Mov- MoS2 and (Mo-S)v-MoS2 materials from the DoS and PDoS calculations using spin-polarized DFT method. The DoS and PDoS of up and down spins states of electrons near the Fermi level are asymmetrically distributed in Mov-MoS2 material as shown in figures 5(a) & 5(c) respectively. Hari Krishna Neupane and Narayan Prasad Adhikari / BIBECHANA 18 (2) (2021) 68-79 74 Fig. 2: (a) Band structure of monolayer MoS2 (b) Band structure of 1S vacancy defect in monolayer MoS2 (c) Band structure of 2S vacancy defects in monolayer MoS2 (d) Band structure of 1Mo vacancy defect in monolayer MoS2 (e) Band structure of (1Mo & 1S) vacancy defects in monolayer MoS2. In all band structure plots, horizontal dotted line represents Fermi energy level. Fig. 3: (a) Total DoS of (3×3) supercell structure of monolayer MoS2 (b) PDoS of up and down spins states of electrons in the individual orbitals of Mo & S atoms in (3×3) supercell structure of MoS2 material. In DoS and PDoS plots, vertical dotted line represents Fermi energy level. Hari Krishna Neupane and Narayan Prasad Adhikari / BIBECHANA 18 (2) (2021) 68-79 75 Fig. 4: (a) Total DoS of up & down spins states of electrons in the orbitals of Mo & S atoms in 1S vacancy defect in MoS2 material (b) Total DoS of up & down spins states of electrons in the orbitals of Mo & S atoms in 2S vacancy defects in MoS2material (c) PDoS of up & down spins states of electrons in the individual orbital of Mo & S atoms in 1S vacancy defect MoS2 material (d) PDoS of up & down spins states of electrons in the individual orbital of Mo & S atoms in 2S vacancy defects MoS2 material. In DoS and PDoS plots, vertical dotted line represents Fermi energy level. Hari Krishna Neupane and Narayan Prasad Adhikari / BIBECHANA 18 (2) (2021) 68-79 76 Fig. 5: (a) Total DoS of up & down spins states of electrons in the orbitals of Mo & S atoms in 1Mo vacancy defect in MoS2 material (b) Total DoS of up & down spins states of electrons in the orbitals of Mo & S atoms in (1Mo & 1S) atoms vacancy defects MoS2material (c) PDoS of up & down spins states of electrons in the individual orbital of Mo & S atoms in 1Mo vacancy defect in MoS2 material (d) PDoS of up & down spins states of electrons in the individual orbital of Mo & S atoms in (1Mo & 1S) atoms vacancy defects MoS2 material. In DoS and PDoS plots, vertical dotted line represents Fermi energy level. This is because, electron’s spins degeneracy of the bands due to Mo vacancy defects, bands are broken and splited. As a result, Mov-MoS2 material bears magnetic properties. We have also calculated the magnetic moments given by spins of electrons in 4p, 4d & 5s orbitals of Mo atoms and 3s & 3p orbitals of S atoms having values 0.03 µB/cell, 0.73 µB/cell & 0.03 µB/cell; and 0.04 µB/cell & 1.89 Hari Krishna Neupane and Narayan Prasad Adhikari / BIBECHANA 18 (2) (2021) 68-79 77 µB/cell in Mov-MoS2 material respectively. Hence, total value of magnetic moment in Mov-MoS2 material is 2.72µB/cell. From above calculations, we know that spins states of electrons in 4d orbital of Mo atoms, and 3p orbital of S atoms have dominant contributions for magnetism. Similarly, the spins states of electrons in the orbital of Mo & S atoms of (Mo-S)v-MoS2 material near the Fermi energy level are asymmetrically distributed in DoS and PDoS plots as shown in figures 5(b) & 5(d) respectively. Magnetic moment is given by spins states of electrons in 4p, 4d & 5s orbitals of Mo atoms; and 2s & 2p orbitals of S atoms; in structure have values 0.01 µB/cell, 0.23 µB/cell & 0.01 µB/cell; and 0.02 µB/cell & 0.72 µB/cell respectively. The total magnetic moment in (Mo-S)v-MoS2 material has value 0.99 µB/cell. Therefore, (Mo-S)v- MoS2 material has magnetic properties. 4d orbital of Mo and 3p orbital of S atoms give greater values of magnetic moment than magnetic moment given by other orbitals of atoms in the material. Magnetic moment of Mov-MoS2 is higher than that of (Mo- S)v-MoS2 material because unequal unpaired (dangling) bonds are present in structures. These dangling bonds are formed due to the effects of 1Mo atom vacancy defects and (1Mo & 1S) atoms vacancy defects in the materials. It is also seen that spins polarization of atoms in (1Mo &1S) atoms vacancy defects structure is less than 1Mo atom vacancy defects structure. 4. Conclusions and Concluding Remarks The novel properties in MoS2 material are developed due to Mo and S atoms vacancy defects. The electronic and magnetic properties of 1Sv- MoS2, 2Sv-MoS2, Mov-MoS2 and (Mo-S)v-MoS2 materials are studied through first-principles calculations within the frame work of spin- polarized DFT method using computational tool quantum ESPRESSO. We have prepared stable structures of these materials, and then analyzed their band structures, DoS and PDoS calculations. From the band structure calculations, we found that 1Sv-MoS2 and 2Sv-MoS2 materials have open small energy band gap of value 0.68 eV and 0.58 eV in both up and down spins electronic states, which implies that 1Sv-MoS2 and 2Sv-MoS2 resemble with the nature of semiconductors. Thus, conductivity of material increases with increase in its defects concentrations. On the other hand, Mov-MoS2 and (Mo-S)v-MoS2 materials have metallic properties because bands around the Fermi level mix with the orbital’s of Mo vacancy in Mov-MoS2, and (Mo & S) vacancies in (Mo-S)v-MoS2. The states associated with the dangling bond and reconstructed Mo-S bond of vacancy occurs near the top of valence band and in conduction band, and appear as flat bands. The charge densities associated in these bands are localized. From the analysis of DoS and PDoS calculations, we found that MoS2, 1Sv-MoS2 and 2Sv-MoS2 materials have non-magnetic properties. The non-magnetic MoS2 material changes to magnetic Mov-MoS2 and (Mo- S)v-MoS2 materials, due to 1Mo atom vacancy defects in monolayer MoS2 and (1Mo & 1S) atoms vacancy defects in monolayer MoS2 structure respectively. Total magnetic moment of Mov-MoS2 and (Mo-S)v-MoS2 materials have values 2.72 µB/cell and 0.99 µB/cell respectively. Significant values of magnetic moment are obtained due to the distribution of electrons spins in 4p, 4d, & 5s orbitals of Mo atoms and 3s & 3p orbitals of S atoms in both materials. Acknowledgments Hari Krishna Neupane and Narayan Prasad Adhikari acknowledge the UGC Nepal award no. PhD-75/76-S&T-09 and grants CRG 073/74 -S&T -01 respectively. Also, Narayan Prasad Adhikari acknowledges network project NT-14 of ICTP/OEA. References [1] J. C. Lei, X. Zhang, and Z. Zhou, Recent advances in MXene: Preparation, properties, and applications, Frontiers of Physics 10(3) (2015) 276- 286. Hari Krishna Neupane and Narayan Prasad Adhikari / BIBECHANA 18 (2) (2021) 68-79 78 [2] M. E. Dávila, et al., Germanene: a novel two- dimensional germanium allotrope akin to graphene andsilicene, New Journal of Physics 16(9) (2014) 095002. [3] S.N.Balendhran, et al., Bhaskaran, Elementalanalogues of graphene: silicene, germanene, stanene, and phosphorene small 11(6) (2015) 640-652. [4] E. S. Kadantsev, and P. 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