First-principles calculations of the dispersion of surface phonons of the unreconstructed and reconstructed Pt(110)

TL;DR

This study uses density functional theory to calculate surface phonon dispersion curves for Pt(110), analyzing both unreconstructed and reconstructed surfaces, and finds that reconstruction is not caused by phonon instability.

Contribution

First-principles calculations of surface phonon dispersions for Pt(110) considering reconstruction effects using linear response theory.

Findings

Reconstruction not driven by phonon instability.

Phonon modes explained by zone folding.

Bulk-like behavior after three layers.

Abstract

We present result of calculations of the surface phonon dispersion curves for Pt(110) using density functional theory in the local density approximation and norm conserving pseudopotentials in a mixed-basis approach. Linear response theory is invoked and both the unreconstructed, and the missing row (1x2) reconstructed surfaces are considered. We find that the reconstruction is not driven by a phonon instability. Most of the observed phonon modes for the (1x2) structure can be understood in terms of simple folding of the (1x1) Brillouin zone onto that for the (1x2) surface. Largest changes in the phonon frequencies on surface reconstruction occur close to the zone boundary in the (001) direction. Detailed comparison of atomic force constants for the (1x1) and the (1x2) surfaces and their bulk counterparts show that the bulk value is attained after three layers. Our calculations reproduce nicely the Kohn anomaly observed along the (110) direction in the bulk. We do not find a corresponding effect on the surface.