Suman Kalyan Sahoo

DFT study of H2O adsorption on TiO2 (110) and SnO2 (110) surfaces

The structure and energetics of water adsorption on the rutile TiO2(110) and SnO2(110) are investigated using the spin-polarized density functional theory formalism. The electron-ion interaction term is described by the projector augmented wave method and the generalized gradient approximation scheme has been adopted to calculate the total energy. The results reveal that in both surfaces, the H2O molecules prefer the 5-fold metal site (Ti or Sn). However, there is a significant difference in the adsorption behavior in terms of chemical bonding. While for TiO2(110) surface, water molecules are adsorbed without losing its molecular identity, on the SnO2(110) surface water molecules prefer dissociative adsorption.

Interaction of ammonia with semiconducting oxide surfaces

Using density functional theory (DFT) we have investigated the adsorption of NH3 molecule on the rutile SnO2(110) and mixed Sn0.5Ti0.5O2(110) surfaces. NH3 molecule gets absorbed on the 5-coordinated Sn atom (Sn5c) of the surface in tilted mode having an additional hydrogen bond with nearby surface bridged oxygen (Obr) atom. After adsorption, 3a1 molecular orbital of ammonia undergo significant dispersal as it donates its electron to surface atoms. The adsorption energy is found to be 1.4-1.6eV. Inclusion of Ti atoms in the SnO2 lattice leads to decrease in the adsorption energy value.Using density functional theory (DFT) we have investigated the adsorption of NH3 molecule on the rutile SnO2(110) and mixed Sn0.5Ti0.5O2(110) surfaces. NH3 molecule gets absorbed on the 5-coordinated Sn atom (Sn5c) of the surface in tilted mode having an additional hydrogen bond with nearby surface bridged oxygen (Obr) atom. After adsorption, 3a1 molecular orbital of ammonia undergo significant dispersal as it donates its electron to surface atoms. The adsorption energy is found to be 1.4-1.6eV. Inclusion of Ti atoms in the SnO2 lattice leads to decrease in the adsorption energy value.

Platinum atomic wire encapsulated in gold nanotubes: A first principle study

The nanotubes of gold incorporated with platinum atomic wire have been investigated by means of firstprinciples density functional theory with plane wave pseudopotential approximation. The structure with zig-zag chain of Pt atoms in side gold is found to be 0.73 eV lower in energy in comparison to straight chain of platinum atoms. The Fermi level of the composite tube was consisting of d-orbitals of Pt atoms. Further interaction of oxygen with these tubes reveals that while tube with zig-zag Pt prefers dissociative adsorption of oxygen molecule, the gold tube with linear Pt wire favors molecular adsorption.

Adsorption of Eu atom at the TiO2 anatase (101) and rutile (110) surfaces

Here we report the adsorption behavior of Eu ad-atom on the TiO2 surfaces. For this purpose we have considered both anatase (101) and rutile (110) planes. All calculations have been carried out using the plane-wave pseudo-potenial approach under the density functional theory formalism. To locate the most stable position of the Eu atom on the surface an extensive geometry optimization was carried out by placing the Eu atoms at various well defined sited on the TiO2 surfaces. On the basis of the energetic it is inferred that on both anatase and rutile surfaces the Eu adatom prefers to be at the higher co-ordination site with difference in binding strength, which is estimated to be 0.37 eV, the anatase being the favored one.

Transition metal dimer on Au(111) surface: A first principle study

The adsorption behaviour of transition metal dimers M2 (M= Cu, Ag, Au) on the Au(111) surface have been studied using the density functional theory formalism. The projector augmented wave method under the spin polarized version of generalized gradient approximation scheme was employed to calculate the total energy. The results suggest that all dimers prefer to orient in parallel to the surface plane, where two M atoms are adsorbed on two nearby threefold fcc sites. We have investigated the chemical interaction between M atoms and Au surface through electronic density of state analysis. It is found that on deposition, the electronic density of states (EDOS) of M2 dimer becomes broader in comparison to their gas phase spectrum.