Abstract
Natural diamond tools experience wear during cutting of steel. As reported in our previous work, Ga doping of diamond has an effect on suppressing graphitization of diamond which is a major route of wear. We investigate interstitial and substitutional dopants of different valence and different ionic radii (Ga, B, and He) to achieve a deeper understanding of inhibiting graphitization. In this study, ab initio calculations are used to explore the effects of three dopants that might affect the diamond wear. We consider mechanical effects via possible solution strengthening and electronic effects via dopant-induced modifications of the electronic structure. We find that the bulk modulus difference between pristine and doped diamond is clearly related to strain energies. Furthermore, boron doping makes the resulting graphite with stable sp2 hybridization more perfect than diamond, but Ga-doped diamond needs 2.49 eV to form the two graphene-like layers than only one layer, which would result in the suppressed graphitization and reduced chemical wear of the diamond tool.
Highlights
In the 21st century, miniaturization has gained rising importance owing to the increasing demand for higher precision and further downsizing of various devices
We reported in a previous study that gallium doping reduced diamond tool wear when cutting steels [Lee et al (2019)]
We investigate ab initio calculations, using density functional theory, the effects of doping that might affect the diamond wear
Summary
In the 21st century, miniaturization has gained rising importance owing to the increasing demand for higher precision and further downsizing of various devices. We computed the defect formation energies (Ef), strain energies (Es), bulk moduli BM, and electronic structures For both I and S configurations, the energy required to dope the material is represented by Ef which is expressed as follows: In the case of substitutional doping: Ef. where M represents the dopant (B, Ga, or He). In order to exclude the effect of a single vacancy defect on the strain energy, the dopant is replaced by a C atom with the same fractional coordinates in the case of S-doping, while the structure remains distorted. To assess the effects of dopants on the diamond mechanical properties, we computed the bulk moduli BM. The effect of doping on the surface energy can be related to stability against exfoliation (graphitization) (Lee et al, 2019)
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