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C2-Si:a Novel Silicon Allotrope in Monoclinic Phase
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作者 Qing-yang Fan Yi-chao Sun +3 位作者 Fang Yang Yan-xing Song Xin-hai Yu si-ning yun 《Chinese Journal of Chemical Physics》 SCIE EI CAS CSCD 2022年第6期945-956,I0073,共13页
Based on density functional theory(DFT),a new silicon allotrope C2-Si is proposed in this work.The mechanical stability and dynamic stability of C2-Si are examined based on the elastic constants and phonon spectrum.Ac... Based on density functional theory(DFT),a new silicon allotrope C2-Si is proposed in this work.The mechanical stability and dynamic stability of C2-Si are examined based on the elastic constants and phonon spectrum.According to the ratio of bulk modulus and shear modulus,C2-Si has ductility under ambient pressure;compared with Si_(64),Si_(96),I4/mmm and h-Si6,C2-Si is less brittle.Within the Heyd-Scuseria-Ernzerhof(HSE06)hybrid functional,C2-Si is an indirect narrow band gap semiconductor,and the band gap of C2-Si is only 0.716 eV,which is approximately two-thirds of c-Si.The ratios of the maximum and minimum values of the Young’s modulus,shear modulus and Poisson’s ratio in their 3D spatial distributions for C2-Si are determined to characterize the anisotropy.In addition,the anisotropy in different crystal planes is also investigated via 2D representations of the Young’s modulus,shear modulus,and Poisson’s ratio.Among more than ten silicon allotropes,C2-Si has the strongest absorption ability for visible light. 展开更多
关键词 Silicon allotrope ANISOTROPY Narrow band gap Elastic constant
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tP40 carbon: A novel superhard carbon allotrope
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作者 Heng Liu Qing-Yang Fan +3 位作者 Fang Yang Xin-Hai Yu Wei Zhang si-ning yun 《Chinese Physics B》 SCIE EI CAS CSCD 2020年第10期392-400,共9页
In this work, a novel carbon allotrope tP40 carbon with space group P4/mmm is proposed. The structural stability, mechanical properties, elastic anisotropy, and electronic properties of tP40 carbon are investigated sy... In this work, a novel carbon allotrope tP40 carbon with space group P4/mmm is proposed. The structural stability, mechanical properties, elastic anisotropy, and electronic properties of tP40 carbon are investigated systematically by using density functional theory (DFT). The calculated elastic constants and phonon dispersion spectra indicate that the tP40 phase is a metastable carbon phase with mechanical stability and dynamic stability. The B/G ratio indicates that tP40 carbon is brittle from 0 GPa to 60 GPa, while tP40 carbon is ductile from 70 GPa to 100 GPa. Additionally, the anisotropic factors and the directional dependence of the Poisson's ratio, shear modulus, and Young's modulus of tP40 carbon at different pressures are estimated and plotted, suggesting that the tP40 carbon is elastically anisotropic. The calculated hardness values of tP40 carbon are 44.0 GPa and 40.2 GPa obtained by using Lyakhov–Oganov's model and Chen's model, respectively, which means that the tP40 carbon can be considered as a superhard material. The electronic band gap within Heyd–Scuseria–Ernzerhof hybrid functional (HSE06) is 4.130 eV, and it is found that the tP40 carbon is an indirect and wider band gap semiconductor material. 展开更多
关键词 novel carbon allotrope elastic properties ANISOTROPY superhard material
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A novel superhard boron nitride polymorph with monoclinic symmetry
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作者 Qing-Yang Fan Chen-Si Li +2 位作者 Ying-Bo Zhao Yan-Xing Song si-ning yun 《Communications in Theoretical Physics》 SCIE CAS CSCD 2022年第6期159-167,共9页
In this work,a new superhard material named Pm BN is proposed.The structural properties,stability,mechanical properties,mechanical anisotropy properties,and electronic properties of Pm BN are studied in this work.Pm B... In this work,a new superhard material named Pm BN is proposed.The structural properties,stability,mechanical properties,mechanical anisotropy properties,and electronic properties of Pm BN are studied in this work.Pm BN is dynamically and mechanically stable,the relative enthalpy of Pm BN is greater than that of c-BN,and in this respect,and it is more favorable than that of T-B_(3)N_(3),T-B_(7)N_(7),tP24 BN,Imm2 BN,Ni As BN,and rocksalt BN.The Young's modulus,bulk modulus,and shear modulus of Pm BN are 327 GPa,331 GPa,and 738 GPa,respectively,and according to Chen's model,Pm BN is a novel superhard material.Compared with its original structure,the mechanical anisotropy of Young's modulus of Pm BN is larger than that of C14 carbon.Finally,the calculations of the electronic energy band structure show that Pm BN is a semiconductor material with not only a wide band gap but also an indirect band gap. 展开更多
关键词 boron nitride polymorph superhard material wider band gap semiconductor firstprinciples calculations
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P2_(1)3 BN:a novel large-cell boron nitride polymorph
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作者 Qing-Yang Fan Nan Wu +4 位作者 Shuai-Ming Chen Li Jiang Wei Zhang Xin-Hai Yu si-ning yun 《Communications in Theoretical Physics》 SCIE CAS CSCD 2021年第12期159-167,共9页
A new boron nitride polymorph,P2_(1)3 BN(space group:P2_(1)3),is investigated by first-principles calculations,including its structural properties,stability,elastic properties,anisotropy and electronic properties.It i... A new boron nitride polymorph,P2_(1)3 BN(space group:P2_(1)3),is investigated by first-principles calculations,including its structural properties,stability,elastic properties,anisotropy and electronic properties.It is found that the new boron nitride polymorph P2_(1)3 BN is mechanically,dynamically and thermodynamically stable.The bulk modulus(B),shear modulus(G)and Young’s modulus of P2_(1)3 BN are 91 GPa,41 GPa and 107 GPa,respectively,all of which are larger than that of Y carbon and TY carbon.By comparing with c-BN,the Young’s modulus,shear modulus and Poisson’s ratio of P2_(1)3 BN show tiny anisotropy in the(001),(010),(100)and(111)planes.At the same time,in contrast with most boron nitride polymorphs,P2_(1)3 BN is a semiconductor material with a smaller band gap of 1.826 eV.The Debye temperature and the anisotropic sound velocities of P2_(1)3 BN are also investigated in this work. 展开更多
关键词 boron nitride polymorph elastic properties ANISOTROPY electronic properties
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