J. Anton

Theoretical predictions of adsorption behavior of elements 112 and 114 and their homologs Hg and Pb

Fully relativistic (four-component) density-functional theory calculations were performed for elements 112 and 114 and their lighter homologs, Hg and Pb, interacting with gold systems, from an atom to a Au(n) cluster simulating the Au(111) surface. Convergence of the adatom-metal cluster binding energies E(b) with cluster size was reached for n>90. Hg, Pb, and element 114 were found to preferably adsorb at the bridge position, while element 112 was found to preferably adsorb at a hollow site. Independently of the cluster size, the trend in E(b) is Pb>>114>Hg>112. The obtained E(b) for Pb and element 112 are in good agreement with the measured adsorption enthalpies of these elements on gold, while the Hg value is obviously underestimated, confirming the observation that adsorption takes place not on the surface but in it. A comparison of chemical bonding in various systems shows that element 114 should be more reactive than element 112: A relative inertness of the latter is caused by the strong relativistic stabilization of the 7s atomic orbital. On the contrary, van der Waals bonding in element 114 systems should be weaker than in those of element 112 due to its larger radius.

Adsorption of CO on cluster models of platinum Ñ111Ö: A four-component relativistic density-functional approach

We report on results of a theoretical study of the adsorption process of a single carbon oxide molecule on a Platinum (111) surface. A four-component relativistic density functional method was applied to account for a proper description of the strong relativistic effects. A limited number of atoms in the framework of a cluster approach is used to describe the surface. Different adsorption sites are investigated. We found that CO is preferably adsorbed at the top position.

Adsorption of superheavy elements on metal surfaces

Fully relativistic four-component density functional theory with the general gradient approximation calculations have been performed to determine the adsorption energy and position of the superheavy element 112 on a Au surface. Extended cluster as well as embedded cluster calculations were used to simulate the surface which allow for the top, bridge, and hollow adsorption sites without losing the advantage of symmetry considerations. Comparison with analogous calculations of the adsorption of the homologue element Hg allows to predict the adsorption of element 112 at a bridge site with a binding energy of 0.67 eV.

Theoretical predictions of trends in spectroscopic properties of gold containing dimers of the 6p and 7p elements and their adsorption on gold.

Fully relativistic, four-component density functional theory electronic structure calculations were performed for the MAu dimers of the 7p elements, 113 through 118, and their 6p homologs, Tl through Rn. It was shown that the M-Au bond strength should decrease from the 6p to 7p homologs in groups 13 and 14, while it should stay about the same in groups 15 through 17 and even increase in group 18. This is in contrast with the decreasing trend in the M-M bond strength in groups 15 through 17. The reason for these trends is increasingly important relativistic effects on the np AOs of these elements, particularly their large spin-orbit splitting. Trends in the adsorption energies of the heaviest elements and their homologs on gold are expected to be related to those in the binding energies of MAu, while sublimation enthalpies are closely connected to the binding energies of the MM dimers. Lack of a correlation between the MAu and MM binding energies means that no correlation can also be expected between adsorption enthalpies on gold and sublimation enthalpies in groups 15 through 17. No linear correlation between these quantities is established in the row of the 6p elements, as well as no one is expected in the row of the 7p elements.

Use of the DV Xα-Method in the Field of Superheavy Atoms

Abstract: We are discussing our manner to calculate the total energy for small molecules within the DV-Xα approximation by using only the monopol part of the potential in the solution of the Poisson equation. A discussion of the relativistic effects including our results for heavy diatomic molecules, is followed by remarks on the choice of the exchange-correlation potential together with our results of calculations on molecules for the element 106 their chemical interpretation. We conclude with results on very heavy correlation diagrams for collision systems with a united Z above 110.

Theoretical predictions of properties of group-2 elements including element 120 and their adsorption on noble metal surfaces.

Trends in properties of group-2 elements Ca through element 120 and their M(2) and MAu dimers were determined on the basis of atomic and molecular relativistic density functional theory calculations. The relativistic contraction and stabilization of the ns AO with increasing atomic number were shown to result in the inversion of trends both in atomic and molecular properties in group 2 beyond Ba, so that element 120 should be chemically similar to Sr. Due to the same reason, bonding in (120)(2) and 120Au should be the weakest among the considered here M(2) and MAu. Using calculated dissociation energies of M(2), the sublimation enthalpy, ΔH(sub), of element 120 of 150 kJ/mol was estimated via a correlation between these quantities in group 2. Using the M-Au binding energies, the adsorption enthalpies, ΔH(ads), of element 120 of 172 kJ/mol on gold, 127 kJ/mol on platinum, and 50 kJ/mol on silver were estimated via a correlation with known ΔH(ads) in the group. These moderate values of ΔH(ads) are indicative of a possibility of chromatography adsorption studies of element 120 on these noble metal surfaces.

Response to “Comment on ‘Four-component relativistic density functional calculations of heavy diatomic molecules’ ” [J. Chem. Phys. 113, 2506 (2000)]

We reply to the comment on our paper “Four-component relativistic density functional calculations of heavy diatomic molecules” [J. Chem. Phys. 112, 3499 (2000)] in which the values of our calculated spectroscopic constants for heavy diatomic molecules were reinvestigated. We point out that the improved spectroscopic constants presented by Liu and van Wullen confirm our basic conclusion that the generalized gradient approximations tend to overcorrect errors of the bond lengths calculated by the local density approximation for molecules with heavy constituents.

Calculation of inner shell excitation in the collision system Ni--Pb

Using an R-dependent atomic basis for static molecular calculations we get accurate single particle energies and dynamic coupling matrix elements. We present our ab initio calculations of inner shell vacancy production for the scattering systems Ni11+-Pb at 1.5 MeV/N and Pb42+-Ni at 1.4 MeV/N.

Inner-shell couplings in transiently formed superheavy quasimolecules

The inner-shell couplings for Uq+-ions (73≤q≤91) moving moderately slow at ~69 MeV u−1 and bombarding thin Au targets have been investigated. Having established the definite survival probability of incoming projectile K vacancies in these targets in an earlier publication, the transfer of these vacancies to the target K-shell due to inner-shell couplings has been studied. As the system is in the quasiadiabatic collision regime for the K-shell of collision partners, advanced SCF-DFS (self-consistent field-Dirac–Fock–Slater) multielectron level diagrams have been used for interpretation. Using a simple model, the L–K shell coupling interaction distance has been estimated and compared with level diagram calculations.

A unified time-dependent description of ion-atom collisions

Abstract We describe electron transfer, excitation and ionization in many electron ion-atom collisions as a time-dependent process in a generalized ansatz by using explicit translational factors and internuclear distance-dependent optimized atomic basis functions. This description allows an automatic adaption of the basis to the energy of the electrons in the collision. As a first example we present results on one- and two-electron ionization in the two electron system p on He.