Study On Interaction Of Atom,Molecule And Cluster In Momentum Space

Atom,molecule and cluster and their interaction with photo/electron is an important research topic during past decades.The Compton profile of the target atom/molecule reveals the electron density distributions in momentum space and very sensitive to the accuracy of wavefunction in the position space.Thus Compton profile can be as a tool to image the electron distribution in atom/molecular as well as can be used to describe the collisional cross section of the resonance transfer of the ion-electron collision through the X-ray decay process?RTEX?.The first part of the thesis focuses on the theoretical calculation of Compton profile of atom/molecule.?1?For atom,we first solve the Compton profile problem of the H atom by analytical method.Then Compton profile of the H atom also studied by using the density functional theory at B3LYP/STO-3G and B3LYP/STO-6G levels.Comparison between present calculations with other theoretical calculations demonstrate that the choice of the basis set has a big influence on the calculation of the Compton profile.?2?For molecule,we calculated the Compton profile of the H₂molecule using the density functional theory at B3LYP/6-311G level.Present calculation compares well with calculation thus can be extended to other molecules such as N₂.The second part of this thesis focuses on the total electrostatic potential endohedral fullerenes.?1?Ab initio calculations of total electrostatic potential of C₆₀have been performed.By comparing the results of density functional theory,MP2 and different basis sets,we analyzes the reason for the difference between the previous works and we find that the B3LYP/6-31G?d?is an effective method for describing the electrostatic potential of C₆₀.?2?Ab initio calculations of total electrostatic potential of C₆₀⁺and C₆₀^-have been performed at the B3LYP/6-31G?d?level,which should be used to recalculate the photoionization cross section of Xe@C₆₀⁺to explain the relevant experiments?PRL,2010,105?21??:213001).?3?For the first time,we obtained the total electrostatic potential of C₂₀,C₈₀0 and C₃₆6 fullerenes.The data obtained are expected to be useful for modelling endohedral fullerenes both for atomic dynamic processes such as photoionization and elastic scattering and for molecular dynamics purpose.