Carbon vacancies in titanium carbide

Abstract

The calculation of vacancy energy in TiC was carried out incorrectly. The curves of the vacancy formation energy as a function of concentration are incorrect, and should be as shown in figure 1. The most important consequence is that the vacancy formation is always positive, thus the earlier conclusion that vacancies should form spontaneously even at absolute zero is no longer valid. Additionally, the stated c/a ratio of the WC form of TiC predicted by the tight binding model was incorrect, as was the energy difference between the WC and NaCl structure types. These should be: optimum c/a = 0.67 and E (WC) - E (NaCl) = 0.21 eV/atom. Figure 1.

Force-based many-body interatomic potential for ZrC

“…1͑c͒. Although there is appreciable charge transfer from Zr to C (0.42 electron͒, 12 it occurs in an isolated sd band 3.4 eV below the main band 17 with metallic screening neutralizing its effect. Ionic bonding and the original metal-metal dd bonds are sufficiently weak in ZrC that they can be neglected in the first approximation.…”

“…Currently there exists no empirical potential model of ZrC or any other refractory carbides, although a tightbinding description has been developed for TiC. 11,12 To accomplish this goal we have adopted an empirical approach based on first understanding the nature of ZrC bonding, then proposing an inspired functional form for the interaction, followed by fitting the parameters to a selected database of properties.…”

The stability of TiC surfaces in the environment with various carbon chemical potential and surface defects

“…[26] Thus, in order to estimate the influence of surface vacancies on the surface energy and relative stability of these low-index surfaces, the p(2×2) surfaces with mono-or di-vacancies of C and Ti are considered. The top views of these defective surfaces are given in Fig.…”

“…[24] A systematic study about the effect of the vacancies on the properties of TiC bulk has been carried out. [25][26][27][28][29][30] For example, the vacancy effect on the structural and electronic properties of TiC bulk has been investigated using a full-potential linear augmented plane-wave method. [29] The interactions of point defects and their role on the thermal stability of TiC bulk have been elucidated using first-principles calculations.…”

Influence of ordered carbon‐vacancy networks on the electronic structures and elastic properties of Nb4AlC3−x

“…It is well recognized that carbon vacancy in binary carbides would strengthen the bonds in the vicinity of vacancies. 38,39 As discussed in the following, introduction of carbon vacancy leads to the relaxation of carbon-vacant Nb 6 C octahedrons and the strengthening of one thirds Nb3-C2 around the vacancy. The carbon vacancies prefer to occupy the 3NN sites rather than the 1NN or 2NN sites (1NN and 2NN stand for the firstand second-nearestneighboring, respectively) to maximize the bond strengthening effect 40 and lower the energy.…”