==========================================
Theoretical surface physics - Bjørk Hammer
==========================================

--------------

Recent research projects by `Bjørk
Hammer: <http://www.phys.au.dk/~hammer>`__

--------------

|links1|

| 
| We are conducting research within theoretical surface science.

| One of the major challenges is to understand how surfaces of metal,
| alloys and compounds react with gas molecules.

| Here an H2 molecule is reacting at a gold surface. The reaction is
| hindered by a large energy barrier reflecting the nobleness of the
  surface.

`Nature 376, 238 (1995). <gold.abstract.html>`__

--------------

| |links2|
| Here the chemical bonding of CO at a Pt surface
| is investigated. Even though we normally think
| of Pt as a noble metal, it is actually capable
| of forming strong bonds to some molecules and
| atoms.

| The molecular orbitals are changed dramatically
| upon adsorption of the CO molecule at a metal
| surface. In particular the 2pi\* orbital of the
| CO which is empty in the gas phase is found to
| change upon adsorption. It aquires a considerable
| filling and is responsible for much of the
| bonding of the molecule to the surface.

`Phys. Rev. Lett. 76, 2141 (1996). <co.abstract.html>`__

--------------

| |links3|
| Our newest studies show that the reactivity of
| atomic step edges is much higher than the
| reactivity of planar surfaces. In terms of
| the reaction rate at room temperature, a
| Ru step edge atom is up to 10 orders of magnitude
| more reactive for breaking of an NO molecular
| bond compared to a Ru(0001) atom.

`Phys. Rev. Lett. 83, 3681 (1999). <rulet.html>`__

--------------

| |links4|
| The description of the surface properties of
| metals, alloys, and compounds and of the
| reaction properties of molecules requires a
| most accurate calculational method. We use
| the density functional theory method founded
| by Nobel laureate, W. Kohn. The electron-
| electron exchange-correlation interaction
| is approximated in the theory and is under
| constant development.

| We have recently proposed a new exchange-
| correlation description (RPBE) which is
| proving to be very accurate both for the
| surface properties and for the molecular
| bond energies. In particular, the overbinding
| of small molecules is reduced as is the
| overbinding of adsorbates at surfaces.

`Phys. Rev. B 59, 7413 (1999). <pbe.html>`__

--------------

.. |links1| image:: forside.jpg
   :width: 164px
.. |links2| image:: co.jpg
.. |links3| image:: step.jpg
.. |links4| image:: dft.jpg