Sp. Tang et Aj. Freeman, STABILIZATION OF THE ASYMMETRIC GE DIMER ON SI(100) BY CHARGE-TRANSFER, Physical review. B, Condensed matter, 50(15), 1994, pp. 10941-10946
The DMol first-principles molecular-cluster total-energy and atomic-fo
rce approach is used to study the Ge dimer on the Si(100) surface with
clusters containing up to 85 atoms. It is shown that the Ge asymmetri
c dimer is energetically more stable than the symmetric dimer due to c
harge transfer from a down dimer atom to an up atom even though this a
ccompanies a weakening of the covalent bonding between the dimer atoms
. By calculating the forces on atoms in the first three Si layers and
minimizing the total energy of the cluster, the optimized atomic geome
try is obtained. The calculated dimer height displacement of this buck
led dimer is shown to be 0.60 Angstrom and the tilt angle is 14.2 degr
ees. The magnitude of this buckling lies between the range that was ca
lculated for clean Si(100)2X1 and Ge(100)2X1 using the same approach,
which agrees with the experimental measurements for those surfaces.