The first-principle calculations are performed to investigate the structural,mechanical and electronic properties of titanium borides （Ti2B,TiB and TiB2）.Those calculated lattice parameters are in good agreement wit...The first-principle calculations are performed to investigate the structural,mechanical and electronic properties of titanium borides （Ti2B,TiB and TiB2）.Those calculated lattice parameters are in good agreement with the experimental data and previous theoretical values.All these borides are found to be mechanically stable at ambient pressure.Compared with parent metal Ti （120 GPa）,the larger bulk modulus of these borides increase successively with the increase of the boron content in three borides,which may be due to direction bonding introduced by the boron atoms in the lattice and the strong covalent Ti-B bonds.Additionally,TiB can be regarded as a candidate of incompressible and hard material besides TiB2.Furthermore,the elastic anisotropy and Debye temperatures are also discussed by investigating the elastic constants and moduli.Electronic density of states and atomic Mulliken charges analysis show that chemical bonding in these titanium borides is a complex mixture of covalent,ionic,and metallic characters.展开更多
The density function theory at the B3LYP/6-31G＊ level was employed to study the structures, including the total energies （EZpE）, the geometries, the oxygen balances （OB100）, the dipole moments, of polynitrohexaaz...The density function theory at the B3LYP/6-31G＊ level was employed to study the structures, including the total energies （EZpE）, the geometries, the oxygen balances （OB100）, the dipole moments, of polynitrohexaazaadamantanes （PNHAAs） and the potential candidates of high energy density compounds （HEDCs）. The structural parameters of PNHAAs, such as the the maximum N-NO2 hond length （LBmax）, the least N-N Mulliken population （BN-N）, the least negative charge on the nitro group （QNO2） and OB100, were studied to predict their relative stability or sensitivity （the easiness for initiating a detonation, high sensitivity means low stability）. It was found that the same conclusion was drawn from the four parameters. With the number of nitro groups increasing, the stabilities of these compounds decrease. OB100 failed in identifying the isomers, but the EZpE energy and the dipole moment were considered to give more reliable results for the isomers.展开更多
基金Project(2010JK404) supported by the Education Committee Natural Science Foundation of Shaanxi Province,ChinaProjects(ZK0918,ZK0915) supported by the Baoji University of Arts and Sciences Key Research,China
文摘The first-principle calculations are performed to investigate the structural,mechanical and electronic properties of titanium borides （Ti2B,TiB and TiB2）.Those calculated lattice parameters are in good agreement with the experimental data and previous theoretical values.All these borides are found to be mechanically stable at ambient pressure.Compared with parent metal Ti （120 GPa）,the larger bulk modulus of these borides increase successively with the increase of the boron content in three borides,which may be due to direction bonding introduced by the boron atoms in the lattice and the strong covalent Ti-B bonds.Additionally,TiB can be regarded as a candidate of incompressible and hard material besides TiB2.Furthermore,the elastic anisotropy and Debye temperatures are also discussed by investigating the elastic constants and moduli.Electronic density of states and atomic Mulliken charges analysis show that chemical bonding in these titanium borides is a complex mixture of covalent,ionic,and metallic characters.
基金Ⅴ. ACKN0WLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.10576016 and No.10576030）.
文摘The density function theory at the B3LYP/6-31G＊ level was employed to study the structures, including the total energies （EZpE）, the geometries, the oxygen balances （OB100）, the dipole moments, of polynitrohexaazaadamantanes （PNHAAs） and the potential candidates of high energy density compounds （HEDCs）. The structural parameters of PNHAAs, such as the the maximum N-NO2 hond length （LBmax）, the least N-N Mulliken population （BN-N）, the least negative charge on the nitro group （QNO2） and OB100, were studied to predict their relative stability or sensitivity （the easiness for initiating a detonation, high sensitivity means low stability）. It was found that the same conclusion was drawn from the four parameters. With the number of nitro groups increasing, the stabilities of these compounds decrease. OB100 failed in identifying the isomers, but the EZpE energy and the dipole moment were considered to give more reliable results for the isomers.
