Some properties of As-doped silicene nanoribbons: A DFT study used the Density functional method (DFT) and VASP software to investigate some properties of the structure of silicene nanoribbons after doping asen. There are six structures studied including top, valley, ortho, meta, para and 100% configurations. This work creates new materials for application in science and technology in the future.
Some properties of As-doped silicene nanoribbons: A DFT study Phan Thi Thuy Linh1*, Nguyen Phuc Nhan1, Luu Thuy Trang1, Vuong Ngoc Anh Dai1, Hoang Van Ngoc1 Insitute of Applied Technology, Thu Dau Mot University, Binh Duong province, Vietnam * Coressponding: 1824401020012@student.tdmu.edu.vn ABSTRACT As the counterpart of graphene, silicene becomes a hot spot in low-dimension material application after being recently grown on different metal-lic surfaces Silicene has a low bumpy hexagonal lattice structure with sp2/sp3 mixed orbital hybridization in Si-Si bonds Limiting the quantum size of silicene is a simple and efficient method to extend the bandgap for silicene while keeping the low undulation honeycomb lattice The finite size limitation of 2D silicene can produce 1D silicene nanoribbons (SiNR) This study used the Density functional method (DFT) and VASP software to investigate some properties of the structure of silicene nanoribbons after doping asen There are six structures studied including top, valley, ortho, meta, para and 100% configurations This work creates new materials for application in science and technology in the future KEYWORDS: Silicene nanoribbons, As-doped silicene, doped structure, doping configurations Introduction A new era of low-dimensional materials science has been ushered in since two-dimensional monolayer (2D) graphite structures were successfully synthesized by Greim and Novoselov by mechanical analysis in 2004 [1-3] This first 2D monolayer graphite system is widely known as graphene Graphene is made up of hybridized carbon (C) atoms on sp2 orbitals and arranged in a highly symmetric planar hexagonal lattice [4] The honeycomb lattice structure of graphene can be extended to produce different C allotropes, where graphene can be stacked to form 3D graphite [5], curled to form nano carbon (1D) [6], was cut to form 1D nano carbon [7] and 3D bent to form a 0D fullerene bridge structure [8] The mechanism of orbital hybridization in graphene is that the C-(2s, 2px, and 2py) are hybridized to form stable bonds to form a planar 2D structure, and the C-2pz orbitals remain in the state freely form weak π bonds along the zdirection This demonstrates that the σ and π bonds in graphene are clearly separated, with the π orbitals mainly contributing to the Dirac cone structure in the low energy region near the Fermi level [9] π-conjugation in the wide energy range of graphene produces many new physical properties that have been of interest in many recent studies [10] To date, graphene has been used in various high-performance applications However, the zero frequency band of graphene limits the application potential of graphene for nano-electronic applications To overcome the unfavorable properties of graphene, various methods have been used to widen the bandgap in graphene including surface functionalization [11], atomic doping [12], mechanical strain [13], layered configuration [14], finite-size limitation [15], defect generation [16], and applied external 107 electric field [17] After graphene, much research effort has been focused on graphene-like monoatomic 2D materials such as silicene [18], germanene [19], stanene [20], phosphorene [21], antimonide [22], Where silicene, a 2D graphene-like structure, is made up of silicon atoms arranged in a bumpy honeycomb lattice structure Silience possesses many new physical properties such as graphene [23]; however, silicene exhibits better compatibility in silicon element-based electronic devices than graphene, so silicene has attracted much research to deploy its potential for practical applications [24] Unlike graphene, silicene can only be synthesized through bottom-up epitaxial growing methods because silicon atoms not have a 3D layered structure like graphite The most common method for synthesizing silicene monolayers is the deposition of silicon atoms on metal substrates [25-27] The successful experimental synthesis of silicene monolayers provided experimental evidence for the theoretical predictions of the existence of silicene in 1994 [28] To date, silicene has been deployed in many applications including room-temperature field-effect transistors (FETs) [29], gas sensors [30], and batteries [31] However, the very small bandgap energy of silicene has shown many disadvantages to deploying silicene in electronic devices [32] Therefore, a lot of research has been done to extend the bandgap for silicene including chemical change [33], quantum limit [34], layered configuration [35], mechanical strains study [36], and apply to external schools [37] Among these methods, limiting the quantum size of silicene is a simple and effective method to extend the bandgap for silicene while keeping the low undulation honeycomb lattice The finite size limitation of 2D silicene can produce 1D silicene nano bands (SiNR) with the armchair edge (ASiNR) and zigzag (ZSiNR) forms [38] SiNR with enhanced bandgap energy can completely overcome the main obstacle of silicene for electronic devices [39] Experimentally, SiNR has been successfully synthesized from both top-down and bottom-up methods The top-down method is to cut 2D silicene sheets to form 1D nano silicene [40], while the bottom-up method is to epitaxially grow 1D nano silicene on metal substrates or insulating thin films [41] SiNRs with their outstanding novel physical properties and their good compatibility in silicon-based electronic devices have attracted much interest in the scientific community recently [42] On the other hand, various applications require materials with more diverse physical properties such as large bandgap energies for semiconductors or optoelectronic applications Therefore, diversifying the essential physical properties of 1D silicene nanoribbons to suit various applications is an important issue for science and technology Various methods have been used to diversify the essential physical properties of 1D silicene nanoribbons including chemical doping [43], passivation of edges [44], layered configurations [43], passivation [44], layered configuration [45], creating lattice defects [46], applying external fields [47] and forming heterostructures; Among these methods, the doping method is currently receiving a lot of attention from researchers both at home and abroad Therefore, we focus on studying some properties of Silence Nanoribbons when doped with As in the hope of creating new materials for application in science and engineering 108 Research Methods In this work, we use density functional theory (DFT) to study and VASP software to simulate materials.Density functional theory (DFT) is a theory used to describe the properties of electron systems in atoms, molecules, solids, within the framework of quantum theory In this theory, the properties of the N-electron system are expressed as a function of the electron density of the entire system (which is a function of spatial coordinate variables) instead of a wave function (which is a function of 3N spatial coordinate variables) Therefore, density function theory has a great advantage (and is currently the most used) in computing the physical properties for particular systems from the very basic equations of quantum physics death VASP (Vienna Ab Initio Simulation Packages): is a computer program for simulating materials at atomic size First, VASP was developed by Mike Payne (MIT) The VASP was then brought by Jurgen Hafner to the University of Vienna in Austria in 1989 The main program of VASP is written by Jurgen Furthmuller Jurgen Furthmuller and Georg Kresse joined Institut fur Materialphysik in 1993 Currently, VASP is being developed by Georg Kresse, recent additions include the development of methods commonly used in molecular quantum chemistry to periodic systems VASP has been used by more than 1400 research groups on the basis of a license agreement with the University of Vienna Results and Discussions 3.1 Doped configurations Fig 1a shows the pristine undoped configuration of a silicene nanoribbons unit cell; Fig 1b 1c in the order of top and valley structures with only doped atom; Fig 1d 1e 1f in order the meta, ortho, and para structures all have doped atoms; Fig 1g is a 100% configuration with doped atoms Table The formation energy of the doping configurations Systems E0t(eV) E0p(eV) E0Si (eV) E0As(eV) ΔEf Ortho -70.218542 -69.408218 -0.1353442 0.09662854 0.88775532 Meta -69.795159 -69.408218 -0.1353442 0.09662854 0.46437232 Para -69.991258 -69.408218 -0.1353442 0.09662854 0.66047132 100% -70.866743 -69.408218 -0.1353442 0.09662854 1.69081896 109 Top -69.866698 -69.408218 -0.1353442 0.09662854 0.49719566 Valley -69.783293 -69.408218 -0.1353442 0.09662854 0.41379066 The formation energy [48]: ΔEf = Et – Ep + n*ESi – n*EAs (1) E0t is the energy of the doping system; E0p is the energy of the pristine system; E0si is the energy of the free Si atom; E0As is the energy of the free As atom; ΔEf is the formation energy of the doping configurations The 100% configuration gives the smallest formation energy, so this is the most stable and optimal configuration Fig Top view of the configurations of silicene nanoribbons when doped with asen (a) pristine ; (b) top; (c) valley; (d) meta; (e) ortho; (f) para; (g) 100% Fig Side view of the configurations of silicene nanoribbons when doped with asen 110 (a) pristine ; (b) top; (c) valley; (d) meta; (e) ortho; (f) para; (g) 100% Fig shows side views of the pristine, top, valley, meta, ortho, para, and 100% configurations Looking at the image, we can see the warping of silicene nanoribbons before and after doping 3.2 Energy band structure and state density Fig 3(a) show the original configuration of silicene nanoribbons has a band gap of 0.4eV and this is a semiconductor Fig 3(b) show after doping an As atom for silicene nanoribbons, the top configuration has no band gap because the fermium-level cutting energy bands go from the valence band to the conduction band, so this is a semi-metallic structure Fig 4(a) show after doping an As atom for silicene nanoribbons, the valley configuration has no bandgap because the fermium-level shear bands go from the valence band to the conduction band, so it is a semi-metallic structure And the meta configuration after doping two As atoms shows a bandgap of 0.44eV, so this is a semiconductor Compared with pristine configuration, the bandgap is wider than 0.04eV, so the meta configuration can be applied in semiconductor devices flexibly Fig 4(b) show after doping an As atom for silicene nanoribbons, the valley configuration has no band gap because the fermium-level shear bands go from the valence band to the conduction band, so it is a semi-metallic structure And the meta configuration after doping two As atoms shows a bandgap of 0.44eV, so this is a semiconductor Compared with pristine configuration, the bandgap is wider than 0.04eV, so the meta configuration can be applied in semiconductor devices flexibly Fig Energy band structure (left), state density (right) of the pristine configuration (a) and top configuration (b) 111 Fig Energy band structure (left), state density (right) of the valley configuration (a) and meta configuration (b) Fig Energy band structure (left), state density (right) of the ortho configuration (a) and para configuration (b) Fig show after doping two As atoms for silicene nanoribbons, the ortho and para configurations are both semiconductors when the ortho configuration has a bandgap of 0.34eV narrower than the pristine configuration of 0.07eV; The para configuration has a bandgap of 0.91eV and is wider than the pristine configuration of 0.51eV, so the para configuration can be applied very well in flexible semiconductor devices 112 Fig Energy band structure (left), state density (right) of the 100% configuration (a) and the contribution of Si(s), Si(p) partial states of the pristine configuration (b) Fig 6(a) show after doping six As atoms for silicene nanoribbons, the 100% configuration has a zero band gap, which is a semiconductor Around the Fermi level is the most concentrated states Fig 6(b) show the blue line is the Si(s) states of the silicon atom, and the red line corresponds to the Si(p) states of the silicon atom Si(s) is located at the bottom of the valence band and the top of the conduction band, while the Si(p) states are concentrated mainly at the top of the valence band and the bottom of the conduction band (around the Fermi level) The peak of the highest state (p) of the pristine configuration corresponds to an energy level of ~ -1.8eV The peak of the highest Si(s) state of the pristine configuration corresponds to an energy level of ~9eV Fig The contribution of Si(s), Si(p) partial states of the top configuration (a) and valley configuration (b) Fig 7(a), the peak of the highest Si(p) state of the top configuration corresponds to an energy level of ~-2.6eV, shifting 0.8eV in the negative direction relative to the pristine configuration The peak of the highest Si(s) state of the top configuration corresponds to an energy level of ~113 10eV, shifting 1eV in the negative direction compared to the pristine configuration For Fig 7(b) the peak of the highest Si(p) state of the valley corresponds to an energy of ~-2.5eV, shifting 0.7eV in the negative direction relative to the pristine configuration The peak of the highest Si(s) state of the valley corresponds to an energy level of ~-9.6eV, shifting 0.6eV in the negative direction relative to the pristine configuration The contribution of the Si(p) state of the valley configuration in the formation of the energy band structure is the largest compared to the remaining configurations Fig The contribution of Si(s), Si(p) partial states of the meta configuration (a) and ortho configuration (b) For Fig 8(a), the peak of the highest Si(p) state of the meta configuration corresponds to an energy level of ~ -2.3eV, shifting 0.5eV in the negative direction compared to the pristine configuration The peak of the highest Si(s) state of the meta configuration corresponds to an energy level of ~-9.8eV, shifting 0.8eV in the negative direction compared to the pristine configuration For fig 8(b), the peak of the highest Si(p) state of the ortho configuration corresponds to an energy level of ~-2.3eV, shifting 0.5eV in the negative direction relative to the pristine configuration The peak of the highest Si(s) state of the ortho configuration corresponds to an energy level of ~-9.1eV, shifting 0.1eV in the negative direction compared to the pristine configuration 114 Fig The contribution of Si(s), Si(p) partial states of the para configuration (a) and 100% configuration (b) For Fig 9(a), the peak of the highest Si(p) state of the para configuration corresponds to an energy level of ~-2.8eV, shifting 1eV in the negative direction relative to the pristine configuration The peak of the highest Si(s) state of the para configuration corresponds to an energy level of ~-9eV, which is unchanged from the pristine configuration For Fig 9(b), the peak of the highest Si(p) state of the 100% configuration corresponds to an energy level of ~ 2.6eV, shifting 0.8eV in the negative direction relative to the pristine configuration The peak of the highest Si(s) state of the 100% configuration corresponds to an energy level of ~ -8.9eV, shifting 0.1eV towards the positive direction compared to the pristine configuration The contribution of the Si(s) state of the para configuration in the formation of the energy band structure is the largest compared to the remaining configurations Fig 10 The contribution of As(s), As(p) partial states of the top configuration (a) and valley configuration (b) For Fig 10(a), the peak of the highest As(p) state of the top configuration corresponds to an energy level of ~ -3.5eV The peak of the highest As(s) state of the top configuration corresponds to an energy level of ~-7.7eV For Fig 10(b), the peak of the highest As(p) state of the valley 115 configuration corresponds to an energy level of ~-3eV The peak of the highest Si(s) state of the valley configuration corresponds to an energy level of ~-7.8eV Fig 11 The contribution of As(s), As(p) partial states of the meta configuration (a) and ortho configuration (b) For Fig 11(a), the peak of the As(p) state is the highest of the meta-configuration with an energy level of ~-2.3eV The peak of the highest As(s) state of the meta-configuration corresponding to the energy level is ~-9.9eV For Fig 11(b), the peak of the highest As(p) state of the ortho configuration corresponds to an energy level of ~-4.3eV The peak of the highest Si(s) state of the ortho configuration corresponds to an energy level of ~-8.8eV For Fig 12(a) the peak of the highest As(p) state of the para configuration corresponds to an energy level of ~ -3.4eV The peak of the highest As(s) state of the para configuration corresponds to an energy level of ~-8.2eV For Fig 12(b) the peak of the highest As(p) state of the 100% configuration corresponds to an energy level of ~ -2.5eV The peak of the highest Si(s) state of the 100% configuration corresponds to an energy level of ~-5.2eV The contribution of the As(p) state of the 100% configuration in the formation of the energy band structure is the largest compared to the remaining configurations 116 Fig 12 The contribution of As(s), As(p) partial states of the para configuration (a) and 100% configuration (b) Conclusions The work studies some properties of silicene nanoribbons when doped with As in the hope of creating new materials for application in science and technology There are studied structures including top, valley, meta, ortho, para, 100% conclusions The original configuration of silicene nanoribbons has a bandgap of 0.4eV and this is a semiconductor After doping an As atom for silicene nanoribbons, the top and valley configurations are semi-metallic because there is no band gap due to the fermium-level shear bands going from the valence band to the conduction band After doping two As atoms for silicene nanoribbons, the meta, ortho, and para configurations are all semiconductors Meta and para configurations have a wider extension than pristine configurations, which can be used very well in flexible semiconductor devices After doping six As atoms for silicene nanoribbons, the 100% configuration has a zero bandgap, which is a semiconductor Around the Fermi level is the most concentrated state The contribution of the Si(p) state of the valley configuration in the formation of the energy band structure is the largest compared to the remaining configurations The contribution of the Si(s) state of the para configuration in the formation of the energy band structure is the largest compared to the remaining configurations The contribution of the As(p) state of the 100% configuration in the formation of the energy band structure is the largest compared to the remaining configurations Acknowledgments This research used resources of the high-performance computer cluster (HPCC) at Thu Dau Mot University (TDMU), Binh Duong Province, Vietnam 117 References [1] Novoselov K S et al., Electric field effect in atomically thin carbon films, Science 306, 666-669, 2004 [2] Geim A K, Graphene prehistory, Physica Scripta 146, 14003, 2012 [3] Novoselov K S et al., Two-dimensional gas of massless Dirac fermions in graphene, Nature 438, 197-200, 2005 [4] Zhang C and Liu T, A review on hybridization modification of graphene and its polymer nanocomposites, Chinese Sci Bull 57, 3010–21, 2012 [5] Ahuja R, Auluck S, Trygg J, Wills J M, Eriksson O and Johansson B, Electronic structure of graphite: effect of hydrostatic pressure, Phys Rev B.51, 4813, 1995 [6] Li K et al., Self-assembly of graphene on carbon nanotube surfaces, Sci Rep 3, 2353, 2013 [7] Ren W, Gao L, Liu B, Zhao J and Cheng H-M, Efficient synthesis of graphene nanoribbons sonochemically cut from graphene sheets Nano Res 3, 16–22, 2010 [8] Tang C, Oppenheim T, Tung V C and Martini A, Structure-stability relationships for graphene- wrapped fullerene-coated carbon nanotubes, Carbon 61, 458–66, 2013 [9] Kariyado T and Hatsugai Y, Manipulation of Dirac Cones in mechanical graphene, Sci.Rep 5, 18107, 2015 [10] Phiri J, Johansson L-S, Gane P and Maloney T, A comparative study of mechanical, thermal and electrical properties of graphene-, graphene oxide- and reduced graphene oxide-doped microfibrillated cellulose nanocomposites, Compos Part B Eng 147, 104–13, 2018 [11] Xu X et al., Interfacial engineering in graphene band gap, Chem Soc Rev 47, 305999, 2018 [12] Fan X, Shen Z, Liu A Q and Kuo J-L, Band gap opening of graphene by doping small boron nitride domains, Nanoscale 4, 2157-65, 2012 [13] Gui G, Li J and Zhong J, Band structure engineering of graphene by strain: firstprinciples calculations, Phys Rev B 78 75435, 2008 [14] Tang S, Wu W, Xie X, Li X and Gu J, Band gap opening of bilayer graphene by graphene oxide support doping, RSC Adv 7, 9862-71, 2017 [15] Villamagua L, Carini M, Stashans A and Gomez C V, Band gap engineering of graphene through quantum confinement and edge distortions, Ric di Mat 65, 579-84, 2016 [16] Iyakutti K, Mathan Kumar E, Thapa R, Rajeswarapalanichamy R, Surya V J and Kawazoe Y, Effect of multiple defects and substituted impurities on the band structure of graphene: a DFT study, J Mater Sci Mater Electron 27, 12669-79, 2016 [17] Mak K F, Lui C H, Shan J and Heinz T F, Observation of an electric-field-induced band gap in bilayer graphene by infrared spectroscopy, Phys Rev Lett 102, 256405, 2009 [18] Oughaddou H et al., Silicene, a promising new 2D material, Prog Surf Sci 90, 46–83, 2015 [19] Acun A et al., Germanene: the germanium analogue of graphene, J Phys Condens Matter 27, 443002, 2015 118 [20] Zhu F et al., Epitaxial growth of two-dimensional stanene, Nat Mater 14, 1020–5, 2015 [21] Khandelwal A, Mani K, Karigerasi M H and Lahiri I, Phosphorene-the two-dimensional black phosphorous: properties, synthesis and applications, Mater Sci Eng B 221, 17–34, 2017 [22] Singh D, Gupta S K, Sonvane Y and Lukačević I, Antimonene: a monolayer material for ultraviolet optical nanodevices, J Mater Chem C 4, 6386–90, 2016 [23] Akbari E, Buntat Z, Afroozeh A, Pourmand S E, Farhang Y and Sanati P, Silicene and graphene nanomaterials in gas sensing mechanism, RSC Adv 6, 81647–53, 2016 [24] Kharadi M A, Malik G F A, Khanday F A, Shah K A, Mittal S and Kaushik B K, Reviewsilicene: from material to device applications, ECS J Solid State Sci Technol 9, 115031, 2020 [25] Meng L et al., Buckled silicene formation on Ir(111), Nano Lett 13, 685–90, 2013 [26] Fleurence A, Friedlein R, Ozaki T, Kawai H, Wang Y and Yamada-Takamura Y, Experimental evidence for epitaxial silicene on diboride thin films, Phys Rev Lett 108, 245501, 2012 [27] Vogt P et al., Silicene: compelling experimental evidence for graphene-like twodimensional silicon, Phys Rev Lett 108, 155501, 2012 [28] Takeda K and Shiraishi K, Theoretical possibility of stage corrugation in Si and Ge analogs of graphite, Phys Rev B 50, 14916, 1994 [29] Lima M P, Fazzio A and Silva A J R da, Silicene-based FET for logical technology, IEEE Electron Device Lett 39, 1258–61, 2018 [30] Aghaei S M, Monshi M M and Calizo I, A theoretical study of gas adsorption on silicene nanoribbons and its application in a highly sensitive molecule sensor, RSC Adv 6, 94417–28, 2016 [31] Galashev A Y and Ivanichkina K A, Silicene anodes for lithium - ion batteries on metal substrates, J Electrochem Soc 167, 50510, 2020 [32] Ni Z et al., Tunable band gap in silicene and germanene, Nano Lett 12, 113, 2012 [33] Nakano H, Tetsuka H, Spencer M J S and Morishita T, Chemical modification of group IV graphene analogs, Sci Technol Adv Mater 19, 76–100, 2018 [34] Mehdi Aghaei S and Calizo I, Band gap tuning of armchair silicene nanoribbons using periodic hexagonal holes, J Appl Phys 118, 104304, 2015 [35] Lin S-Y, Liu H-Y, Nguyen D K, Tran N T T, Pham H D, Chang S-L, Lin C-Y and Lin M-F, Stacking-configuration-enriched fundamental properties in bilayer silicenes, SiliceneBased Layer Mater., 5–28, 2020 [36] Jia T-T et al., Band gap on/off switching of silicene superlattice, J Phys Chem C 119, 20747, 2015 [37] Drummond N D, Zólyomi V and Fal’ko V I, Electrically tunable band gap in silicene, Phys Rev B 85, 75423, 2012 [38] Mehdi Aghaei S, Torres I and Calizo I, Structural stability of functionalized silicene nanoribbons with normal, reconstructed, and hybrid edges, J Nanomater., 5959162, 2016 119 [39] Chuan M W, Wong K L, Hamzah A, Riyadi M A, Alias N E and Tan M L P, Electronic properties of silicene nanoribbons using tight-binding approach, International Symposium on Electronics and Smart Devices (ISESD), 1–4, 2019 [40] De Padova P et al., Multilayer silicene nanoribbons, Nano Lett 12, 5500, 2012 [41] van den Broek B, Houssa M, Lu A, Pourtois G, Afanas’ev V and Stesmans A, Silicene nanoribbons on transition metal dichalcogenide substrates: effects on electronic structure and ballistic transport, Nano Res 9, 3394–406, 2016 [42] Li H et al., High performance silicene nanoribbon field effect transistors with current saturation, Eur Phys J B 85, 274, 2012 [43] Sarebanha B and Ahmadi S, Doping effect on spin dependent electron transport in zigzag silicene nanoribbons, Procedia Mater Sci 11, 259–64, 2015 [44] Yao Y, Liu A, Bai J, Zhang X and Wang R, Electronic structures of silicene nanoribbons: two-edge-chemistry modification and first-principles study, Nanoscale Res Lett 11, 371, 2016 [45] Deng X Q and Sheng R Q, Spin transport investigation of two type silicene nanoribbons heterostructure, Phys Lett A, 383, 47–53, 2019 [46] An R-L et al., Vacancy effects on electric and thermoelectric properties of zigzag silicene nanoribbons, J Phys Chem C 118, 21339, 2014 [47] Fang D Q, Zhang Y and Zhang S L, Silicane nanoribbons: electronic structure and electric field modulation, New J Phys 16, 115006, 2014 [48] Q Pang, Y Zhang, J M Zhang, V Ji, and K W Xu, 2011, Electronic and magnetic properties of pristine and chemically functionalized germanene nanoribbons, Nanoscale, Vol (10) p 4330-4338 120 ... [23] Akbari E, Buntat Z, Afroozeh A, Pourmand S E, Farhang Y and Sanati P, Silicene and graphene nanomaterials in gas sensing mechanism, RSC Adv 6, 81647–53, 2016 [24] Kharadi M A, Malik G F A, ... configuration of silicene nanoribbons has a bandgap of 0.4eV and this is a semiconductor After doping an As atom for silicene nanoribbons, the top and valley configurations are semi-metallic because... physical properties for particular systems from the very basic equations of quantum physics death VASP (Vienna Ab Initio Simulation Packages): is a computer program for simulating materials at atomic