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
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
基金supported by the National Natural Science Foundation of China(No.61804120 and No.61901162)the China Postdoctoral Science Foundation(No.2019TQ0243 and No.2019M663646)+3 种基金the Key Scientific Research Plan of Education Department of Shaanxi Provincial Government(Key Laboratory Project)(No.20JS066)the Young Talent Fund of University Association for Science and Technology in Shaanxi,China(No.20190110)the National Key Research and Development Program of China(No.2018YFB1502902)Key Program for International S&T Cooperation Projects of Shaanxi Province(No.2019KWZ-03)。
文摘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.
基金supported by the National Natural Science Foundation of China(Grant No.61804120)China Postdoctoral Science Foundation(Nos.2019TQ0243,2019M663646)+4 种基金Natural Science Basic Research Program of Shaanxi(2021JQ-515)Key scientific research plan of Education Department of Shaanxi Provincial Government(Key Laboratory Project)(No.20JS066)Young Talent fund of University Association for Science and Technology in Shaanxi,China(No.20190110)National Key Research and Development Program of China(No.2018YFB1502902)Key Program for International S&T Cooperation Projects of Shaanxi Province(No.2019KWZ-03)。
文摘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.
