DSpace at VNU: Transition Metal (Fe and Cr) Adsorptions on Buckled and Planar Silicene Monolayers: A Density Functional Theory Investigation

DSpace at VNU: Transition Metal (Fe and Cr) Adsorptions on Buckled and Planar Silicene Monolayers: A Density Functional...

Subscriber access provided by CLARKSON UNIV Article Transition Metal (Fe and Cr) Adsorptions on Buckled and Planar Silicene Monolayers: A Density Functional Theory Investigation Viet Quoc Bui, Tan-Tien Pham, Hoai-Vu Si Nguyen, and Hung Minh Le J Phys Chem C, Just Accepted Manuscript • DOI: 10.1021/jp407601d • Publication Date (Web): 10 Oct 2013 Downloaded from http://pubs.acs.org on October 11, 2013 Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication They are posted online prior to technical editing, formatting for publication and author proofing The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record They are accessible to all readers and citable by the Digital Object Identifier (DOI®) “Just Accepted” is an optional service offered to authors Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts The Journal of Physical Chemistry C is published by the American Chemical Society 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society Copyright © American Chemical Society However, no copyright claim is made to original U.S Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties Page of 35 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The Journal of Physical Chemistry Transition Metal (Fe and Cr) Adsorptions on Buckled and Planar Silicene Monolayers: A Density Functional Theory Investigation Viet Q Bui, Tan-Tien Pham, Hoai-Vu S Nguyen, Hung M Le* Faculty of Materials Science, University of Science, Vietnam National University, Ho Chi Minh City, Vietnam AUTHOR EMAIL ADDRESS hung.m.le@hotmail.com RECEIVED DATE TITLE RUNNING HEAD Transition Metal (Fe and Cr) Adsorptions on Buckled and Planar Silicene Monolayers CORRESPONDING AUTHOR FOOTNOTE Corresponding author: correspondence should be addressed hung.m.le@hotmail.com ACS Paragon Plus Environment to Hung M Le at The Journal of Physical Chemistry 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 ABSTRACT The adsorption of metals on silicene monolayer may potentially offer advantageous applications in electronic and spintronic devices In this study, by employing first-principles calculations, we investigate the attachment of two 3d transition metals (Fe and Cr) on buckled and planar silicene surfaces Besides examining structural stability, we also explore interesting ferromagnetic as well as half-metallic features of the material All Fe adsorption cases are found to be more stable (with the lowest binding energy being 3.39 eV) than Cr adsorption cases When the metal adsorption rate is high, Fe tends to penetrate into both buckled and planar silicene layers This insertion behavior allows the 3d shells of Fe to enhance bonding interactions with all 3px, 3py, and 3pz orbitals of Si, thus produce more stable structures The adsorptions of Cr with high distribution ratio are found to be more stable than the low-Cr-distribution structures It is observed that Cr does not penetrate into the silicene layer like Fe Overall, ferromagnetism is dominant with five nanostructures, while two Cr adsorption cases on planar silicene preferentially behave as anti-ferromagnets, and one Fe adsorption case is non-magnetic From our observation, there is an inversed interplay between structural stability and magnetic moments, i.e FeSix nanostructures (more stable) tend to exhibit lower ferromagnetic moments The half-metallic characteristic is found in four nanostructures, which can be potentially applied in spin-electronic devices The gaps derived from spin-down states for those half-metallic nanostructures vary from 0.28 to 0.57 eV Keywords: silicene, DFT, metal-silicene interaction, magnetism, half-metallic, metal adsorption ACS Paragon Plus Environment Page of 35 Page of 35 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The Journal of Physical Chemistry I INTRODUCTION Advanced two-dimensional (2D) materials have highly attracted attention of the research community for years Silicene,1 one of such interesting materials, is an infinite monolayer of silicon, whose structure is very similar to that of graphene.2 Purely consisting of silicon atoms, silicene can be integrated into electronic components, and is expected to have a great deal of potential applications in electronic transporting devices In the most stable form, each silicon atom in silicene connects to three surrounding others by sp2-sp3-hybridized bonds, which consequently results in a “low-buckled” honeycomb structure.1, 3-5 The electronic structure of silicene has been proved to establish a zero band gap when the bonding (π) and anti-bonding orbitals (π*) are shown to contact at the Dirac point, which consequently results in very high electron mobility.1 Besides the low-buckled structure, first-principles calculations also suggests the existence of planar derivative of silicene, whose structural configuration is even more similar to the conformation of graphene.6, In this study, we investigate the bonding interactions between two different silicene conformations (both low-buckled (B, more stable) and planar (PL, less stable) forms) and two transition metal atoms (Cr and Fe) There have been successful efforts in synthesizing silicene on metal and semiconductor surface for electronic applications Lalmi et al.8 showed an experimental evidence in which silicene had epitaxial development on Ag(111) by condensing a silicon flux on the surface in vacuum condition Nevertheless, those results highly relied on scanning tunneling microscopy (STM) observations, which approximately resulted in a Si-Si distance of 1.9 Å This bond distance was, however, much smaller than the theoretically-predicted value varying in the range of 2.22 to 2.24 Å.1, 9, 10 By employing tunneling microscopy and angular-resolved photoemission spectroscopy in conjunction with first-principles simulations, Vogt et al.11 provided an ACS Paragon Plus Environment The Journal of Physical Chemistry 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 experimental evidence of epitaxial silicene sheets on Ag(111) The distance between Si-Si was then determined as 2.22 Å in such a study, which established consistency with the previous theoretical results.1 In term of metal contact investigations, Feng et al.12 also presented an experimental investigation showing a procedure for synthesizing silicene on Ag(111) Since the early initialization of silicene investigations, computational efforts dedicating to study metal-attached silicene have attained remarkable achievements thanks to the rigorous development of Density Functional Theory (DFT)13, 14 and noticeable efforts in improvement of computational packages for condensed matter calculations There have been several DFT-based investigations conducted to study silicene-metal interactions, especially their coordination chemistry and physical properties In a theoretical work conducted by Sahin and Peeters,15 the attachments of alkali, alkaline-earth, and 3d transition metal atoms were investigated using DFT methods, and several possible absorption positions (hexagonal, bridge, valley, and top sites, as shown in Fig 1) of a metal atom on silicene were suggested It was reported by Dzade et al.16 that many transition metals (such as Ti, Nb, Ta, Cr, Mo, and W) tended to preferably locate on the H site of silicene when they occupied all honeycomb units on the silicene monolayer (with empirical formulas of MSi2) They witnessed that the electronic and magnetic properties of silicene changed significantly due to metal adsorptions Particularly, CrSi2 became a twodimensional magnet and exhibited a strong piezomagnetic property with a magnetic moment in the range of 3.08 and 3.33 µB When inspecting the electronic and magnetic properties as well as interactions of silicene with H and Br, Zheng and Zhang17 reported that the investigated structures displayed either ferromagnetic semiconducting or half-metallic behaviors In this study, we concentrate on two 3d transition metals, Cr and Fe, which are wellknown for their interesting magnetic behaviors Particularly, Fe is known as a ferromagnet, while ACS Paragon Plus Environment Page of 35 Page of 35 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The Journal of Physical Chemistry Cr exhibits spin-density-wave antiferromagnetism.18 In addition, such transition metals are believed to establish stable coordination bonds with two-dimensional structures, such as graphene.19, 20 Being motivated by the recent experimental results of silicene,8, 11, 12, 21-23 in this study, we attempt to conduct a theoretical investigation of structural stability, electronic structure, and magnetic property of two-dimensional metal-silicene nanostructures (MSix, M = Fe, Cr) using a DFT-based approach II METAL-SILICENE ADSORPTION STRUCTURES (MSix) The distribution rates of Cr/Fe on silicene and the silicene conformation itself (B or PL) have a significant impact on the stability of the investigated structures, which can be evaluated by estimating strength of coordination bonds (via binding energy) In this investigation, we study different metal absorption ratios on two silicene conformations (B/PL), which include MSi2(B), MSi2(PL), MSi6(B), and MSi6(PL) as clearly shown in Fig Indeed, the H site is most favored when M adsorbs on either buckled or planar silicene,15 which accordingly produces a twodimensional lattice that has a 2D hexagonal unit cell We first consider metal adsorptions with high M concentration (MSi2(B) and MSi2(PL)) In those structures, M atoms occupy all available honeycomb units of the surface As a result, there are two Si atoms and one M atom in a two-dimensional unit cell In Fig 2(a) and 2(c) respectively representing FeSi2(B) and CrSi2(B), M atoms absorb all honeycomb rings in the low-buckled silicene sheet The nanostructures of FeSi2(PL) and CrSi2(PL) (Fig 2(b) and 2(d), respectively) has one M atom located at the center of every planar honeycomb silicon ring In the case of MSi6(PL) and MSi6(B), there are six Si atoms and one M atom in a primitive hexagonal unit cell The metal atom in these structures tends to occupy a center ACS Paragon Plus Environment The Journal of Physical Chemistry 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Page of 35 honeycomb unit and leave six adjacent (surrounding) units empty (unoccupied) In Fig 2(e) and 2(g), Fe and Cr atoms are respectively located on a low-buckled silicene sheet, while in Fig 2(f) and Fig 2(h), Fe and Cr are located on planar silicene (denoted as FeSi6(PL) and CrSi6(PL), respectively) There are two types of bonding in those structures: coordination bonds between MSi (under the hybridization effect of 3d orbitals of M and 3p orbitals of Si), and Si-Si interactions In the hexagonal unit cell of each investigated nanostructure (with lattice parameter a listed in Table 1), the two-dimensional characteristic orientation is established in the x and y directions The vacuum assumption is constituted in the z direction by employing large lattice parameter c (30 Bohr or 15.87 Å) in all cases III COMPUTATIONAL DETAIL In this study, we employ the Perdew-Burke-Ernzerhof (PBE)24, 25 exchange-correlation functional within generalized gradient approximations and the ultrasoft pseudopotentials26, 27 for Cr, Fe, and Si to perform first-principles calculations All calculations are executed using the Quantum ESPRESSO package.28 In addition, we utilize spin polarization implementation to inspect the electronic and magnetic properties The nanostructures are optimized by relaxing atomic positions and unit-cell vectors simultaneously using the Broyden-Fletcher-Goldfarb-Shanno (BFGS)29 algorithm with the energy and gradient convergence criteria being 10-5 eV and 10-4 eV/Bohr, respectively The kpoint mesh for all hexagonal lattices (with lattice parameter a given in Table I) is selected as (12 × 12 × 1) in all calculations to ensure consistency in total energy calculations, and the kinetic energy cut-off of 45 Rydberg (612 eV) is chosen for plane-wave expansions ACS Paragon Plus Environment Page of 35 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The Journal of Physical Chemistry For each optimized structure, we employ the following formula to analyze the binding energy of M atoms attached on silicene: Ebinding = Esilicene + EM – Estructure (1) where Esilicene, EM, and Estructure are the total energies of silicene, M layer, and the investigated Msilicene adsorption nanostructure given by DFT calculations, respectively IV RESULTS AND DISCUSSION FeSi2(B) and FeSi2(PL) nanostructures In the FeSi2 (as well as CrSi2) structures, the metal atoms occupy all available honeycomb units on buckled/planar silicene Particularly, in FeSi2(B), Fe atoms have a tendency to penetrate into the silicene layer, and interact with both upper and lower Si atoms (as shown in Fig 2(a)) Fe, therefore, forms bonding interactions with the surrounding Si atoms and heavily alters the buckled silicene structure by stretching the Si-Si interaction The Si-Si and Fe-Si distances in FeSi2(B) are 2.60 and 2.27 Å, respectively Recall that in an isolated buckled silicene monolayer, the Si-Si bond is only 2.29 Å, which is much shorter than the Si-Si bond in FeSi2(B) The Fe-Si bond is, however, almost equal to the Si-Si bond in isolated buckled silicene according to our DFT calculations In addition, the buckled gap between the upper and lower Si layers is much distorted (estimated as 1.45 Å), while the original buckled gap in silicene is only 0.45 Å Hence, we believe that such Fe penetration with a high distribution ratio would cause a significant change in structural configuration to the buckled silicene structure Equation (1) is then employed to derive the binding energy, and FeSi2(B) is found to be highly stable with a binding energy of 3.67 eV/cell ACS Paragon Plus Environment The Journal of Physical Chemistry 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Subsequently, spin polarizations are inspected to predict the magnetic property of FeSi2(B) By observing the total density of state (DOS) and the corresponding partial density of state (PDOS) of Fe 3d and Si 3p subshells (as illustrated in Fig 3(a)), we are able to address a non-magnetic behavior (polarization is not found in the DOS) In addition, this nanostructure is believed to be metallic because of electronic state distribution around the Fermi level (positioned at in the plot) We also conceive that the 3d shells of Fe and 3p shells of Si highly overlap, which consequently results in a strong bonding interaction Especially, it can be seen that the electron distribution in 3d z gives a strong peak near the Fermi level, which indicates a high electron accepting behavior of Fe The 3pz subshell of Si, unsurprisingly, overlaps much with 3d orbitals of Fe As mentioned earlier, the penetration of Fe into the silicene layer also allows the metal 3d orbitals to have more interactions with 3px and 3py of Si, and consequently results in high binding stability Furthermore, such geometric configuration in general allows spin-up and spin-down states to form exactly similar interactions and therefore align identically (no spin polarization) This is a unique behavior when Fe is attached on the surface of buckled silicene, and we not observe such similarities in other cases In the FeSi2(PL) structure, Fe is located at the centers of all honeycomb rings in the infinite planar (PL) silicene sheet The occupancy of such metal atoms results in an interwoven network with an infinite planar structure as illustrated in Fig 2(b) At equilibrium, we have found in the relaxed FeSi2(PL) structure that Fe atoms again penetrate into the surface of planar silicene; hence, the resulted structure is perfectly planar and can be considered as the most compressed structure in this investigation We observe that the Si-Si and Fe-Si bond distances are identical (2.33 Å) The Si-Si bond in this case is slightly longer than the Si-Si bonds in an isolated planar silicene sheet (given by our DFT calculations as 2.25 Å) Consequently, the ACS Paragon Plus Environment Page of 35 Page of 35 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The Journal of Physical Chemistry silicene network is slightly loosened under the effect of Fe penetration by 3.4% For comparison purposes, we summarize bonding distances and binding energies of FeSi2(B) and FeSi2(PL) (as well as the other investigated nanostructures) in Table To evaluate structural stability, we subsequently calculate the binding energy of FeSi2(PL) using equation (1) Indeed, its binding energy is 3.76 eV, which is the highest among eight investigated nanostructures In spin-polarized DOS analysis, it can be seen that there is a difference in distributions of the spin-up and spin-down states Unlike the previous structure (FeSi2(B)), we observe ferromagnetism and electron conductivity in FeSi2(PL) In the bonding aspect, when bonding orbitals (3d subshells of Fe and 3p subshells of Si) are analyzed, the overlapping behavior is similar to the previous case study of FeSi2(B) More specifically, the 3d orbitals of Fe strongly hybridize with not only Si 3pz but 3px and 3py orbitals as well However, we not observe equal distributions in spin-up and spin-down states, which adequately produces a small ferromagnetic moment There are two types of magnetic terms reported in this study, i.e the total (MT) and absolute magnetizations (MA) which are derived in the following equations: M T = ∫ (nup − ndown )d 3r (2) M A = ∫ nup − ndown d 3r (3) The total magnetization of FeSi2(PL) indicates ferromagnetism with a magnitude of 1.20 µB/cell, while the absolute magnetization is 1.48 µB/cell For convenience, all total and absolute magnetizations of the investigated nanostructure are summarized and reported in Table A calculation of a × supercell is performed to validate ferromagnetism of this structure In fact, ACS Paragon Plus Environment Page 21 of 35 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The Journal of Physical Chemistry Figure Three possible metal adsorption sites on buckled/planar silicene: hexagonal (H), bridge (B), and top (T) When considering a buckled silicene sheet, there are actually two different T sites, which correspond to the upper and lower Si atoms in the buckled form 21 ACS Paragon Plus Environment The Journal of Physical Chemistry 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Figure Top views and side views of Fe/Cr adsorptions on silicene There are eight investigated nanostructures in this study: (a) FeSi2(B), (b) FeSi2(PL), (c) CrSi2(B), (d) CrSi2(PL), (e) FeSi6(B), (f) FeSi6(PL), (g) CrSi6(B), and (h) CrSi6(PL) The top views are provided to illustrate the distribution ratio of metal on silicene 22 ACS Paragon Plus Environment Page 22 of 35 Page 23 of 35 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The Journal of Physical Chemistry Figure (a) Total DOS and PDOS of the Fe 3d and Si 3p subshells in FeSi2(B), where spin polarization is not observed, (b) Total DOS and PDOS of the Fe 3d and Si 3p subshells in FeSi2(PL) 23 ACS Paragon Plus Environment The Journal of Physical Chemistry 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Figure (a) Total DOS and PDOS of the Cr 3d and Si 3p subshells in CrSi2(B), (b) PDOS of each Cr and all Si atoms CrSi2(PL) In CrSi2(B), we can derive a small band gap of 0.28 eV from the spin-down state CrSi2(PL) is anti-ferromagnetic according to the opposing behavior of electronic states of two Cr atoms (in the supercell) 24 ACS Paragon Plus Environment Page 24 of 35 Page 25 of 35 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The Journal of Physical Chemistry Figure Total DOS and PDOS of Cr and Si atoms when Cr atoms are attached on both sides of (a) buckled and (b) planar silicene In both cases, Cr atoms occupy all honey comb unit of silicene (high distribution rate) The electronic states of two Cr atoms are opposing to each other, which implies anti-ferromagnetism 25 ACS Paragon Plus Environment The Journal of Physical Chemistry 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Figure (a) Total DOS and PDOS of Fe 3d and Si 3p subshells in FeSi6(B), (b) Total DOS and PDOS of Fe 3d and Si 3p subshells in FeSi6(PL) Both nanostructures are shown to be halfmetallic (with band gaps in the spin-down states derived as 0.51 and 0.49 eV, respectively) 26 ACS Paragon Plus Environment Page 26 of 35 Page 27 of 35 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The Journal of Physical Chemistry Figure (a) Total DOS and PDOS of the Cr 3d and Si 3p subshells in CrSi6(B), (b) PDOS of each Cr and Si atoms in a (2 × 1) supercell of CrSi6(PL) CrSi6(PL) can be seen as an antiferromagnet from this plot 27 ACS Paragon Plus Environment The Journal of Physical Chemistry 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Page 28 of 35 Table Lattice parameter a, M-Si, Si-Si bonds, M-silicene interlayer distances, and binding energies of the MSi2(B), MSi2(PL), MSi6(B), and MSi6(PL) nanostructures (with M = Fe, Cr) a (Å) FeSi2(B) Bond distance (Å) Si-Si M-Si M-silicene interlayer distance (Å) Silicene buckled gap (Å) Binding energy (eV/cell) 3.73 2.60 2.27 1.45 3.67 FeSi2(PL) 4.03 CrSi2(B) 3.74 2.33 0.00 3.76 0.95 1.77 CrSi2(PL) 4.01 FeSi6(B) 6.65 2.31 1.11 1.94 0.66 3.49 FeSi6(PL) 6.79 2.24 1.10 3.39 CrSi6(B) 6.71 2.32 0.62 2.61 CrSi6(PL) 6.79 2.27 2.29 2.33 2.52 3.11 2.56 2.38 2.64 2.49 2.50 2.74 2.55 2.82 1.23 0.26 2.64 2.38 2.29 28 ACS Paragon Plus Environment Page 29 of 35 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The Journal of Physical Chemistry Table Total magnetizations, absolute magnetizations, and estimated band gaps of the investigated nanostructures (*anti-ferromagnetic nanostructure) FeSi2(B) FeSi2(PL) CrSi2(B) CrSi2(PL)* FeSi6(B) FeSi6(PL) CrSi6(B) CrSi6(PL)* Total magnetization (µB/cell) 0.00 1.20 4.00 0.00 2.10 2.05 4.00 0.00 Absolute magnetization (µB/cell) 0.00 1.48 4.60 4.15 3.04 2.91 4.69 4.57 Electron conductivity Estimated P metallic metallic half-metallic metallic half-metallic half-metallic half-metallic metallic 0.00 0.56 1.00 0.00 1.00 1.00 1.00 0.00 29 ACS Paragon Plus Environment Band gap (eV) 0.28 0.51 0.49 0.57 The Journal of Physical Chemistry 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Page 30 of 35 Table Main orbital contributions to ferromagnetic/anti-ferromagnetic moments in MSi2(B), MSi2(PL), MSi6(B), MSi6(PL) (M = Fe, Cr) Si 3pz FeSi2(B) FeSi2(PL) CrSi2(B) CrSi2(PL)* FeSi6(B) FeSi6(PL) CrSi6(B) CrSi6(PL)* 0.00 -0.09 -0.30 0.14 -0.31 -0.21 -0.32 0.32 3px (3py) 4s 0.00 -0.01 0.00 0.05 0.02 -0.03 0.06 0.09 0.00 0.04 0.10 0.12 0.05 0.04 0.08 0.09 4p 0.00 0.05 0.13 0.07 0.06 0.04 0.08 0.07 M (Fe, Cr) 3dzx 3d z (3dzy) 0.00 0.77 0.90 0.89 0.54 0.78 0.88 0.87 * Anti-ferromagnetic cases: absolute magnetic contributions are reported 30 ACS Paragon Plus Environment 0.00 0.17 0.84 0.78 0.65 0.54 0.88 0.88 3d x − y (3dxy) 0.00 0.08 0.75 0.63 0.27 0.25 0.67 0.56 (0.72) Page 31 of 35 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 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Chemistry Transition Metal (Fe and Cr) Adsorptions on Buckled and Planar Silicene Monolayers: A Density Functional Theory Investigation Viet Q Bui, Tan-Tien Pham, Hoai-Vu S Nguyen, Hung M Le* Faculty... metals (Fe and Cr) on both buckled and planar silicene surfaces The distribution rate of metal atoms on silicene is taken into account when we consider MSi2 and MSi6 lattice models Overall, eight metal- silicene. .. investigations, computational efforts dedicating to study metal- attached silicene have attained remarkable achievements thanks to the rigorous development of Density Functional Theory (DFT)13, 14 and