Extraction of molecular electron momentum densities from electron density contour maps

Electron momentum densities and Compton profiles for some linear di- and tri-atomic heteronuclear molecules have been extracted from the exclusive knowledge of electron density in the coordinate space, &#961;(<SUB>r</SUB>). The procedure developed is based upon semi-classical considerations. The application of the present method to experimentally available electron dencontour maps is discussed

Refinement of electron momentum densities of ionic solids using an experimental energy constraint

It is demonstrated how one can refine a given approximate momentum density distribution using a constraint of the experimental electronic energy. The technique developed is based on the calculus of variations. This technique has been applied to ionic solids such as LiF, LiCIl NaF, NACl, MgO, KF and KCl

Electron momentum distributions and atomic r<SUP>n</SUP> expectation values

The r<SUP>n</SUP> expectation values have been extracted from the known electron momentum distributions for hydrogen, helium, argon, and krypton atoms with the use of a semiclassical approach. These values compare fairly well with their Hartree-Fock counterparts. This procedure provides a link between the distribution of electrons in the momentum space and that in the coordinate space

Direct and reverse transformations between electron density and electron momentum density: connection with the locally averaged method

It has been established here that the direct transformation from electron density to electron momentum density [Phys. Rev. A 24, 2906 (1981)] is exactly identical to the locally averaged method of Lam and Platzman [Phys. Rev. B 9, 5128 (1974)] for a spherically symmetric, monotonic-decreasing atomic-electron density. However, the former approach brings out more clearly the physical features associated with the momentum density extracted from the electron density and also has the potential to effect reverse transformations

Analysis of atomic electron momentum densities: use of information entropies in coordinate and momentum space

The entropy maximization procedure has been extended to treat simultaneously the densities in coordinate and momentum space. The key quantity to be maximized is the sum of information entropies in complementary spaces rather than the entropy in one space alone. This modified procedure has been used to assess the quality of refined electron momentum densities for He, Be and H2. The momentum density which maximizes the entropy sum yields good estimates of Compton lineshape and related momentum space expectation values

Electron density to electron momentum density: the use of an energy constraint

A modification of the Burkhardt, Kónya, Coulson, and March (BKCM) procedure [Phys. Rev. A 24, 2906 (1981)], enabling an estimation of electron momentum density exclusively from the knowledge of an atomic electron density, has been presented. A known value of the electronic energy has been employed as a constraint in effecting this modification without loss of simplicity of the BKCM procedure. These electron momentum densities are seen to be more physical than their unmodified counterparts

Theoretical investigations on structure, electrostatic potentials and vibrational frequencies of diglyme and Li<SUP>+</SUP>-(diglyme) conformers

The trends for cation binding for several conformers of diglyme are predicted by mapping the topography of the molecular electrostatic potential (MESP) at the Hartree-Fock (HF) level. Different Li<SUP>+</SUP>-(diglyme) geometries derived by exploiting the MESP cooperative effects are used subsequently in ab initio computations. The binding energies for Li<SUP>+</SUP> with diglyme have been calculated in mono-, bi- and tridentate coordinations by employing the HF, second-order Møller-Plesset (MP2) and the hybrid density functional methods. The calculated vibrational spectrum of Li<SUP>+</SUP>-(diglyme) also points to a gauche conformation of diglyme in the complex

From molecular electron density to electron momentum density

The scope of the quasiclassical procedure previously used by us for estimating atomic-electron momentum densities exclusively from the knowledge of electron densities has been extended to diatomic molecules. This procedure yields a spherically averaged molecular-electron momentum density from which the corresponding Compton profile and &lt;p<SUP>n</SUP>&gt; expectation values may be computed. The procedure has been tested for the molecules H<SUB>2</SUB> and N<SUB>2</SUB>. The Compton profiles and &gt;p<SUP>n</SUP>&lt; values thus obtained compare well with their wave-function and experimental counterparts

Hartree-Fock momentum expectation values for atoms and ions

Nonrelativistic (p<SUP>n</SUP>) values are calculated for n = -2, -1, 1, 2, 3, and 4 from the analytic Roothaan-Hartree-Fock atomic wave functions of Clementi and Roetti. Results are tabulated for the ground and certain excited states of the atoms helium through xenon and their singly charged positive and negative ions

Use of energy constraint for refinement of electron momentum distributions

A procedure based on the calculus of variations to refine a given electron momentum density with the constraints of the given number of electrons and a prescribed &lt;p<SUP>2</SUP>&gt; expectation value has been developed. This procedure has been tested with near-Hartree-Fock (NHF) electron momentum density data employed as initial distributions for the atoms beryllium through neon. The constraints of the corresponding CI-theoretical and experimental energy values have been imposed. In all cases, the values of the refined electron momentum density at p=0 and the peak value of the Compton profile J(0) are lower than the corresponding NHF ones. This lowering of J(0) value is generally in conformity with the corresponding results from CI and MC-SCF calculations. The present procedure is seen to simulate well the electron momentum densities and &lt;p<SUP>-1</SUP>&gt; as well as &lt;p&gt; expectation values obtained from correlated wave functions without ever doing extra quantum mechanical calculations