We investigate the structural, electronic and adsorption properties of one single CO molecule adsorbed on RhN （N = 2-19） clusters, using the density-functional theory in the spin-polarized generalized gradient appro...We investigate the structural, electronic and adsorption properties of one single CO molecule adsorbed on RhN （N = 2-19） clusters, using the density-functional theory in the spin-polarized generalized gradient approximation. It is found that the structural growth model of the RhN clusters transforms from double layers （N = 12-16） to three layers （N ： 17-19）. Three different adsorption types are the atop site adsorption for N = 6, 8, 9, 11, 12, the bridge site adsorption for N ： 2-5, 7, 10, 13-15, 17 and the face adsorption for N = 16, 18, 19. The adsorption abilities of RhN clusters are related to C-O bond length, vibrational frequency, adsorption energy and the charge transfer between CO and Rh clusters as well as the electronic density of state. With the increase of Rh cluster size, the adsorption energy of CO adsorbed on RhN clusters tends to be 2.2 eV-2.3 eV, which is 0.2 eV-0.3 eV larger than the theoretical value （about 2.0 eV） of CO molecule adsorption on clean Rh （111） surface.展开更多
For B2 NiAl and NiTi intermetallic compounds, the ideal stress–strain image is lack from the perspective of elastic constants. We use first-principles calculation to investigate the ideal strength and elastic behavio...For B2 NiAl and NiTi intermetallic compounds, the ideal stress–strain image is lack from the perspective of elastic constants. We use first-principles calculation to investigate the ideal strength and elastic behavior under the tensile and shear loads. The relation between the ideal strength and elastic constants is found. The uniaxial tension of NiAl and NiTi along <001> crystal direction leads to the change from tetragonal path to orthogonal path, which is driven by the vanishing of the shear constant C(66). The shear failure under {110}{111} shear deformation occurring in process of tension may result in a small ideal tensile strength(~ 2 GPa) for NiTi. The unlikeness in the ideal strength of Ni Al and Ni Ti alloys is discussed based on the charge density difference.展开更多
The structures under different pressures, elastic properties, electronic structures and lattice vibrations of the X_2N_2O（X = C, Si, Ge） compounds are investigated by using the first-principle method. Based on the p...The structures under different pressures, elastic properties, electronic structures and lattice vibrations of the X_2N_2O（X = C, Si, Ge） compounds are investigated by using the first-principle method. Based on the phonon density of state,the thermodynamic properties of the present compounds are studied under different pressures and at different temperatures. The structural parameters including the bond lengths and bond angles are in agreement with available experimental measurements and theoretical calculations. We employ the elastic theory to calculate the nine independent elastic constants（C_（ij）） and the derived elastic moduli（B, G, E, v）. Results indicate that these X_2N_2O（X = C, Si, Ge） compounds are mechanically stable and show the brittle behaviors. The electronic properties of the present compounds are analyzed by using the band structure and density of states. The phonon dispersion calculations imply that the present compounds are dynamically stable. Based on the quasi-harmonic approximation, the calculations of the specific heat indicate that the temperature in a range of 0 K–1500 K and pressure in a range of 0 GPa–40 GPa have a large effect on the thermal quantities of Ge_2N_2O,compared with on those of the C_2N_2O and Si_2N_2O compounds.展开更多
基金supported by the National Basic Research Program of China (Grant No. 2011CB606401)
文摘We investigate the structural, electronic and adsorption properties of one single CO molecule adsorbed on RhN （N = 2-19） clusters, using the density-functional theory in the spin-polarized generalized gradient approximation. It is found that the structural growth model of the RhN clusters transforms from double layers （N = 12-16） to three layers （N ： 17-19）. Three different adsorption types are the atop site adsorption for N = 6, 8, 9, 11, 12, the bridge site adsorption for N ： 2-5, 7, 10, 13-15, 17 and the face adsorption for N = 16, 18, 19. The adsorption abilities of RhN clusters are related to C-O bond length, vibrational frequency, adsorption energy and the charge transfer between CO and Rh clusters as well as the electronic density of state. With the increase of Rh cluster size, the adsorption energy of CO adsorbed on RhN clusters tends to be 2.2 eV-2.3 eV, which is 0.2 eV-0.3 eV larger than the theoretical value （about 2.0 eV） of CO molecule adsorption on clean Rh （111） surface.
基金Project supported by the Science Challenge Project,China(Grant No.TZ2018002)the Fundamental Research Funds for the Central Universities,China(Grant No.FRF-TP-18-013A3)。
文摘For B2 NiAl and NiTi intermetallic compounds, the ideal stress–strain image is lack from the perspective of elastic constants. We use first-principles calculation to investigate the ideal strength and elastic behavior under the tensile and shear loads. The relation between the ideal strength and elastic constants is found. The uniaxial tension of NiAl and NiTi along <001> crystal direction leads to the change from tetragonal path to orthogonal path, which is driven by the vanishing of the shear constant C(66). The shear failure under {110}{111} shear deformation occurring in process of tension may result in a small ideal tensile strength(~ 2 GPa) for NiTi. The unlikeness in the ideal strength of Ni Al and Ni Ti alloys is discussed based on the charge density difference.
基金Project supported by the Fundamental Research Funds for the Central Universities,China(Grant No.FRF-TP-14-029Al)
文摘The structures under different pressures, elastic properties, electronic structures and lattice vibrations of the X_2N_2O（X = C, Si, Ge） compounds are investigated by using the first-principle method. Based on the phonon density of state,the thermodynamic properties of the present compounds are studied under different pressures and at different temperatures. The structural parameters including the bond lengths and bond angles are in agreement with available experimental measurements and theoretical calculations. We employ the elastic theory to calculate the nine independent elastic constants（C_（ij）） and the derived elastic moduli（B, G, E, v）. Results indicate that these X_2N_2O（X = C, Si, Ge） compounds are mechanically stable and show the brittle behaviors. The electronic properties of the present compounds are analyzed by using the band structure and density of states. The phonon dispersion calculations imply that the present compounds are dynamically stable. Based on the quasi-harmonic approximation, the calculations of the specific heat indicate that the temperature in a range of 0 K–1500 K and pressure in a range of 0 GPa–40 GPa have a large effect on the thermal quantities of Ge_2N_2O,compared with on those of the C_2N_2O and Si_2N_2O compounds.
