Based on first-principle calculations, electronic structure and optical properties of a single-walled zigzag SiC nanotube with silicon antisite defect have been investigated. This defect results in the formation of a bump in the surface of the nanotube. No defect energy level is formed in its band gap, which is originated from the resonance between the defect level and conduction band resulting in the defect level entering its conduction band. The most primary dielectric peak in dielectric function parallel to the axis of the nanotube is depressed, while the first peak perpendicular to its axis is enhanced. These results are meaningful for investigations on SiCNT electronic and optical devices.

Antisite defects are common defects in nanotube materials and have seriously impacts on their electronic properties. Based on density-functional theory calculations, the electronic structures of the antisite defective chiral (6, 2) SiCNTs are investigated. C antisite and Si antisite lead to the formation of a depression and a bump in the surface of the nanotube, respectively. In the band gap of the SiCNT with a C antisite defect, the occupied level near the top of the valence band is formed, while the unoccupied level originating from the Si antisite defect enters the conduction band of the SiCNT.

Mining activities would generate large scale goaf, and the existing of goaf makes the mountain body produce great distortion. Therefore, it has become a kind of serious geological hazard. Based on the concrete conditions of Yanchi Mountain, the simulation with ANSYS was conducted for analyzing the stability of goaf, mine pillar and roof, which would find out the high stress zone and plastic zone of the goaf. Therefore, the conclusion that inadequate of the pillar strength is the main cause of the mountain deformation is drawn, and a new strengthening method which is to strengthen the mine pillar and to increase new mine pillars is put forward on basis of the conclusion.The results show that the strengthening method has an obvious effect, and it reduces the workload and the cost, which also provides very significant evidence for the future studying.

Vacancy defects are common defects formed in the syntheses of silicon carbide nanotubes (SiCNTs) and seriously impact the electronic structures of the nanotubes. With first-principle calculations based on density functional theory (DFT), vacancy defective (6,2) SiCNTs are studied. Vacancies form a pair of fivefold and ninefold rings. Carbon vacancy introduces an occupied defect level near the top of the valence band and an unoccupied level in the conduction band. Three defect levels are found in the band gap of the SiCNT with a silicon vacancy. These results are helpful for investigations on SiCNT devices and sensors.