First-principles Study On Doping Properties And Derived Configurations Of Diamondene

Due to the rich bond structure of carbon atoms,there are varieties of carbon allotropes formed,such as graphite,diamond,fullerene,carbon nanotubes,graphene,etc.These carbon allotropes have very prominent and unique physical properties,which greatly promote the development of materials,physics,chemistry,biology and other related fields.Recently,Chernozatonskii et al.proposed a new carbon allotrope,diamane(diamondene),which is the thinnest sp3 hybrid diamond film.Because of the excellent electrical properties,optical properties,thermal conductivity and mechanical properties,diamondene attracted extensive attentions in the field of carbon materials.High pressure is an important method for synthesizing diamond.Diamond synthesized by high pressure can be preserved to atmospheric pressure and has a wide range of industrial applications.However,diamondene synthesized by high-pressure method cannot be stored at room pressure.An important question in this field is:how to stabilize diamondene synthesized under high pressure at ambient condition?Since the radii of B atom and N atom are equivalent to C atom,it is easier to achieve B doping and N doping in carbon systems.Besides,B dopant and N dopant make carbon materials multifunctional materials with different properties,improving the application value of carbon materials in various fields.Inspired by this,we introduced B dopant and N dopant into diamane to study its effects on structural stability,synthesis pressure,and physical properties.In addition,the most widely studied configuration of diamondene are based on compressing bilayer graphene to form interlayer bonds.But diamondene is the thinnest sp3 hybrid diamond film.So the mininum repeating unit of bulk diamond in all directions may be in the configuration of diamondene.Therefore,we extended the structure of diamondene based on bulk diamond,and found that one of the configurations derived a novel class of novel quasi-two-dimensional carbon materials.This paper aims to these two scientific issues on how to enhance the stability of diamondene and explore the derived structure of diamondene.Based on density functional theory,the research on the structure,stability,electronic properties,and elastic properties of doped diamane and new configurations is carried out.The followings are the main resreatch contents of our studies:1.Boron-dopant enhanced stalibity of diamane with tunable band gap.B atom tends to stay in the substitutional site,and the most stable configuration is the structure with vertical B-B dimer.The formation energy of B-doped diamane is lower than the counterpart of pristine diamane indicating that B dopant can facilitate the synthesis of diamane.The configurations with vertical B-B dimers are semiconductors with tunable band gaps,which decrease with the B concentration increasing due to the interaction between B-B dimers.Moreover,configurations with meta-stable B distributions are metals,which have comparable superconducting transition temperatures with B-doped diamond(-4 K).These results can give instructions to experiments for synthesizing the B-doped diamane with different properties.A metallic B-doped diamane can be obtained by compressing one pristine graphene and one B-doped graphene,and a semiconductor may can be synthesized via the pressurization of bi-layer B-doped graphene.This work firstly proposed the introduction of heteroatom doping in diamane to study its effect on structural stability,and confirmed that the existence of B-B interlayer bonds could reduce the formation energy of H-adsorbed bilayer graphene to diamond.B dopant helps diamane to exist stably at ambient condition.This work opens up a new idea for the future research on the stabilization mechanism of diamane.2.Configuration stability and electronic properties of diamane with boron and nitrogen dopants.The N atom tends to stay in the substitutional site rather than the interstitial site,and the most stable configuration is the structure where the N atom is located at the external substitutional site without H saturation.The B and N atoms co-doped in diamane tend to gather to form a covalent bond,where N is saturated by H,since the stability of a lone pair of electrons in N is reduced by the B dopant.Moreover,B and N dopants can adjust the bandgap(0-3.52 eV)and reduce the formation energy of diamane to promote its synthesis.The formation energies of Ndoped diamane are not sensitive to N distributions,and diamane containing a vertical B-N bond has the lowest FE due to the attraction between the N-dopant-induced electron and the B-dopant-induced hole.This work provides a new way to experimentally synthesize more stable and functional diamane.3.Configuration stability and physical properties of new diamondene structure.In this work,by extending diamondene structure to the minimum repeating unit of bulk diamond along different crystal orientations,the configuration stability and physical properties of 21 kinds of diamondene were systematically investigated based on first-principles methods,and effects of hydrogen saturation were also presented.It was found that diamondene formed by compressing layered graphene would graphitized,and surface adsorption of H atoms could prevent the graphitization.The configuration with stepped surface is restructured to reduce the energy,while the configuration with open surface is not dynamically stable even if all dangling bonds are saturated.The electronic properties of diamondene can be adjusted by the concentration of H atoms with the bandgap varying from 0 eV to 3.45 eV,and some configurations exhibit ferromagnetism or anti-ferromagnetism.Moreover,diamondene has a high Young’s modulus comparable to bulk diamond.Particularly,the configuration containing dumbbell units is twice as hard as diamond.The formation energies of all stable diamondene configurations were illustrated.Furthermore,the instability law of two-dimensional carbon structure was systematically discussed,which is important for designing new carbon allotropes.4.New quasi-2D carbon materials with nano-thickness based on diamondene.A new class of quasi-two-dimensional carbon materials with nanometer thickness derived from the structure optimization of the diamondene configuration obtained by cutting hexagonal diamond along the(102)crystal plane.The new structure could be regarded as carbon nanotubes arranged in parallel with shared wall,which containing the structural features of graphene,carbon nanotubes,and diamond.The density functional theory with periodic conditions was applied to investigate the structural,electronics,elastic,and vibrational properties.These two structures have dynamic stability,thermodynamic stability and mechanical stability.The armchair structure presents a nonmagnetic semiconductor with the band gap of 1.204 eV;the zigzag structure exhibits an antiferromagnetic semiconductor(0.646 eV),and its ferromagnetic configuration(metallic state)could realize directional transport.The new structure has a strong anisotropy with a maximum value of 865 GPa and 1018 GPa for armchair and zigzag configuration,respectively,which is comparable to that of diamond.The analysis of Raman spectrum reveals the specific vibrational signatures of these two structures,which could be used to identify the existence of such materials in experimental studies.The new structure has large pores and is highly anisotropic,which has broad application prospects in the fields of energy storage,catalysis,ultrasensitive sensors,and new composite materials.