Adsorption characteristics of magnesium atoms on phosphorus-doped single-walled silicon nanotubes (SWSiNTs) are studied using plane wave pseudopotential method with generalized gradient approximation based on density functional theory. Adsorption energies of magnesium atoms on pure,phosphorus-doped and deformation effects (compressive or tensile) (6,6) SWSiNTs are calculated. Bond and Mulliken population of both pure and phosphorus-doped SWSiNTs are also analyzed.It shows that covalent bond and ionic bond conexist in armchair silicon nanotube superlattices doped with phosphorus atoms by forming ionic bond of Mg-P and Si-P,and enhancing ionic bond of Si-Si. Adsorption energy of Mg atom on SWSiNTs are improved significantly by doping phosphorus atoms. Adsorption energy are also increased under compressive deformation at 0.25%,0.50%,1.00%,1.25% and tensile deformation at 1.00%,1.25%. It enhances adhesion of interface of silicon nanotubes as reinforce combined with matrix.

CASTEP program based on density functional theory was employed to study adsorbing of Fe on N doping carbon nanotube rings under deformation. It shows that bonding energy of new construction is negative, which satisfying energy conditions of stable existence. Adsorbing energies of Fe are enhanced since activities of doping system are increased to form Fe-N covalent bonds easily. Increasing stretch and compression deformations linearly, adsorbing energies of Fe reduce rapidly in parabola shape. They are more sensitive to stretch deformations.

Atom module of α-Fe [100](010) edge dislocation is built in metallic matrix of ductile cast iron. Density functional theory CASTEP method is employed to calculate energy parameters of carbon doping edge dislocation system including atom embedded energy,affinity energy and Mulliken population. It shows that there exist C_2v symmetry group in structure of α-Fe [100](010) edge dislocation and localized effect of dislocation happens in limited range. Energy valley attracts light impurity carbon which forms atom clusters in dislocation corn. Interaction between C and Fe atoms is strengthened with charge transportation between C-4s and Fe-2p obtains which pins dislocation slipping. Mulliken population of Fe atom and C atom is high. Length is short. Iron carbide could be produced. Binding energy and PDOS of carbon doping cementite system show that silicon promotes cementite decomposing and nicalon becomes corn of graphite ball,which improve impact toughness of ductile cast iron.