Rumpled relaxation of TiC(001) and TaC(001) determined by high-resolution medium-energy ion scattering spectroscopy

Abstract

The rumpled relaxations of TiC͑001͒ and TaC͑001͒ with strong covalent bonds were determined precisely by medium energy ion scattering using a toroidal electrostatic analyzer with an excellent energy resolution of ⌬E/Eϭ9ϫ10 Ϫ4 . It allows a monolayer depth resolution and thus a simple triangulation method using the ion shadowing effect achieved the accuracy of 0.01 Å in depth for the displacement of atoms near a surface region. The surface relaxation ͑ϩ: outwards͒ and rumpling ͓ϩ: displacement of C toward vacuum side larger than that of Ti͑Ta͔͒ were estimated to be ϩ0.1Ϯ0.3% and ϩ3.5Ϯ0.5% for TiC͑001͒ and ϩ1.4Ϯ0.3% and ϩ4.9Ϯ0.5% for TaC͑001͒. The present result is consistent with the recently reported calculation using the full-potential linear muffin-tin orbital method but inconsistent with the predictions using the tight-binding model and the full-potential linearized augmented plane-wave method.

Efficient noble metal nanocatalysts supported on HfC(001) for O2 dissociation

“…[34][35][36][37][38] The stability of the three low-index Miller surfaces has been studied in detail for HfC, 39 which is consistent with previous theoretical studies for the HfC surfaces 40,41 that the (001) surface is the most stable one. These calculations have provided a large number of insights and helped to answer the long standing questions about the interpretation of experimental measurements.…”

Ab initio study of Fe adsorption on the (001) surface of transition metal carbides and nitrides

“…First, we obtained the surface energies for the (0 0 1) face of MX phases in a good agreement with previous pseudopotential plane-wave-based DFT results (Table 1). We found that c s is higher for (0 0 1)MC than for (0 0 1 As obtained in numerous theoretical [29,[35][36][37][38][39][40][41][42][43] and experimental [44][45][46][47][48] studies as well as demonstrated in our calculations (Table 1), the free MX(0 0 1) surface exhibits a rippled relaxation, where the topmost X and M atoms are displaced outward and inward with respect to the atomic positions in bulk. The displacements of X atoms (d X ) are less than those of M atoms (d M ) in all MX except for the Group V TM nitrides (VN, NbN, and TaN).…”

First-Principles Studies of Antiferromagnetic MnO and NiO Surfaces

“…42,43) For the transition metal nitrides and carbides, outward displacement of anion was reported from the first-principles calculations, 44,45) which is consistent with the previous experiments. 46) In case of oxides such as MgO, outward displacement of O has been reported by theory [47][48][49] and experiments. 50) However, surface rumpling of monoxide is too small to measure, especially for the stable (001) surface.…”