Chemistry & Biochemistryhttps://aurora.auburn.edu/handle/11200/442092024-06-18T06:37:34Z2024-06-18T06:37:34ZElectron binding energies and Dyson orbitals of Al(5)O(m)(-) (m=3,4,5) and Al(5)O(5)H(2)(-)https://aurora.auburn.edu/handle/11200/499632021-02-01T20:07:03ZElectron binding energies and Dyson orbitals of Al(5)O(m)(-) (m=3,4,5) and Al(5)O(5)H(2)(-)
Photoelectron spectra of Al5Om
− m=3–5 and of the anion produced by the dissociative adsorption
of a water molecule by Al5O4
− are interpreted with density-functional geometry optimizations and
electron-propagator calculations of vertical electron detachment energies. For Al5O3
−
, Al5O4
−
, and
Al5O5H2
−
, the observed signals may be attributed to the most stable isomer of each anion. For Al5O5
−
,
the features in the photoelectron spectrum are due to three almost isoenergetic isomers.
Assessment of transition operator reference states in electron propagator calculationshttps://aurora.auburn.edu/handle/11200/499622021-02-01T20:07:00ZAssessment of transition operator reference states in electron propagator calculations
The transition operator method combined with second-order, self-energy corrections to the electron
propagator TOEP2 may be used to calculate valence and core-electron binding energies. This
method is tested on a set of molecules to assess its predictive quality. For valence ionization
energies, well known methods that include third-order terms achieve somewhat higher accuracy, but
only with much higher demands for memory and arithmetic operations. Therefore, we propose the
use of the TOEP2 method for the calculation of valence electron binding energies in large molecules
where third-order methods are infeasible. For core-electron binding energies, TOEP2 results exhibit
superior accuracy and efficiency and are relatively insensitive to the fractional occupation numbers
that are assigned to the transition orbital.
OH3- and O2H5- double Rydberg anions: Predictions and comparisons with NH4- and N2H7-https://aurora.auburn.edu/handle/11200/499612021-02-01T20:06:58ZOH3- and O2H5- double Rydberg anions: Predictions and comparisons with NH4- and N2H7-
A low barrier in the reaction pathway between the double Rydberg isomer of OH3
− and a
hydride-water complex indicates that the former species is more difficult to isolate and characterize
through anion photoelectron spectroscopy than the well known double Rydberg anion DRA,
tetrahedral NH4
−
. Electron propagator calculations of vertical electron detachment energies VEDEs
and isosurface plots of the electron localization function disclose that the transition state’s electronic
structure more closely resembles that of the DRA than that of the hydride-water complex. Possible
stabilization of the OH3
− DRA through hydrogen bonding or ion-dipole interactions is examined
through calculations on O2H5
− species. Three O2H5
− minima with H− H2O2, hydrogen-bridged, and
DRA-molecule structures resemble previously discovered N2H7
− species and have well separated
VEDEs that may be observable in anion photoelectron spectra.
Surface Green’s function calculations: A nonrecursive scheme with an infinite number of principal layershttps://aurora.auburn.edu/handle/11200/499602021-02-01T20:06:56ZSurface Green’s function calculations: A nonrecursive scheme with an infinite number of principal layers
A novel computational method for a surface Green’s function matrix is introduced for the
calculation of electrical current in molecular wires. The proposed nonrecursive approach includes an
infinite number of principal layers and yields the second-order matrix equation for the transformed
Green’s function matrix. The solution is found by the direct diagonalization of the auxiliary matrix
without any iteration process. As soon as complex roots of the auxiliary matrix Gˆ S are
calculated, the gaps and the bands in the surface electronic structure are found. It is shown that the
solution of a second-order matrix equation determines the spectral density matrix, that is, the density
of states for noninteracting electrons. Single and double principal layer models are studied both
analytically and numerically. The energy interval for nonvanishing spectral matrices is determined.
This method is applicable to matrices of any rank.