Part Of Spin Density Research Articles

Atomic and molecular forms of oxygen on Ag(331). Theoretical analysis using the DFT method

Oxygen adsorption on Ag(331) is analyzed in a cluster approximation using the density functional theory (DFT) method. Adsorption centers (AC) for the bridge (S2) and three-center (S3) coordinations of oxygen are identified on the stepwise face Ag(331) and the Ag-O bond energies at these centers are calculated. For atomic adsorption, the Ag-O bond strength varies from 50 to 65 kcal/mole, depending on AC. The heat of molecular adsorption DH = 5 kcal/mole for S2(L1-L2) type AC. The molecule is oriented parallel to Ag(110) between the terraces with R(O-O) = 1.34 a Calculations showed that the ground state of the O2Ag20(331) system is a triplet, but a part of spin density is delocalized on silver atoms, so that the spin density on oxygen ρs(O) = 0.46 (ρs = 1.0 for the free O2 molecule). The energy of the singlet state is 9 kcal/mole greater than that of the ground state.

A projection operator method for the analysis of magnetic neutron form factors

A set of projection operators in matrix form has been derived on the basis of decomposition of the spin density into a series of fully symmetrized cubic harmonics. This set of projection operators allows a formulation of the Fourier analysis of magnetic form factors in a convenient way. The presented method is capable of checking the validity of various theoretical models used for spin density analysis up to now. The general formalism is worked out in explicit form for the fcc and bcc structures and deals with that part of spin density which is contained within the sphere inscribed in the Wigner-Seitz cell. This projection operator method has been tested on the magnetic form factors of nickel and iron.