Calorimetric Measurement of the Energy Difference Between Two Solid Surface Phases

Abstract

A recently designed single-crystal surface calorimeter has been deployed to measure the energy difference between two solid surface structures. The clean Pt{100} surface is reconstructed to a stable phase in which the surface layer of platinum atoms has a quasi-hexagonal structure. By comparison of the heats of adsorption of CO and of C(2)H(4) on this stable Pt{100}-hex phase with those on a metastable Pt{100}-(1x1) surface, the energy difference between the two clean phases was measured as 20 +/- 3 and 25 +/- 3 kilojoules per mole of surface platinum atoms.

Mechanism and Dynamics of the CO-Induced Lifting of the Pt(100) Surface Reconstruction

“…This can be justified when one realizes that CO binds only to the Pt surface through the C atom. Further, in vacuum, the hex phase is predicted by our MEAM potential to be favored over the 1 1 phase by 0:1 eV=atom, which agrees reasonably well with the experimental value of 0:2 eV=atom [21].…”

Relativistic tight-binding model: Application to Pt surfaces

“…The SR-SCTB 5 × 1 reconstruction energy is almost 0.4 eV /atom higher than the one reported for the DFT calculation. Our SR-SCTB calculation of the 5 × 29 reconstruction energy is quite close to the value reported experimentally for the hexagonal reconstruction 41 . The structure of the SR-SCTB derived reconstructions is also somewhat different from that obtained from DFT calculations, as shown in Fig.…”

“…In both cases we used a surface slab of 5 atomic layer instead of the 9 layers used in the low index face relaxation studies, in order to reduce computational cost. The results of our SR-SCTB calculations for the hexagonal reconstructions are presented in Table IV, along with the results of DFT calculations 47,49 by others and an experimental result for the surface energy 41 . One can see that the SR-SCTB results for geometrical properties, like surface corrugation and the interplanar distance change are in very good agreement with the DFT results for the 5 × 1 reconstruction.…”

Theoretical study of pattern formation during the catalytic oxidation of CO on Pt{100} at low pressures

“…Low energy electron diffraction ͑LEED͒ intensity measurements have determined the activation barrier for the conversion of the clean surface from 1 ϫ 1 to hex to be 115 kJ/ mol of surface platinum atoms. 13 Following Yeo et al, 8 we reproduce their schematic potential energy diagram ͑Fig. 1͒ relating the clean surface phases and the two CO-covered surface phases.…”

“…7 The energy difference between the two clean solid surfaces has been measured calorimetrically and found to be 20 kJ/ mol of surface platinum atoms ͑and equivalent to 0.21 eV per 1 ϫ 1 area͒. 8 This procedure relies on the fact that adsorption of several gases can induce or lift the surface reconstruction, thereby allowing the construction of thermodynamic cycles that provide a direct measurement of the heat of reconstruction.…”