1:30 PM - 3:30 PM
▲ [18p-P2-6] Ab Initio Exploration of Diamond Doping and Its Possible Effect on Mechanical Properties
Keywords:Diamond, doping, ab initio modeling
Doping of diamond, specifically with ions such as Ga+ was reported to influence the machining performance of diamond tools during cutting of ferrous materials. We investigate ab initio, using Density Functional Theory, the effects of doping that might affect the diamond wear. We consider mechanical effects via possible solution strengthening as well as electronic effects via dopant-induced modifications of the band alignment at the diamond-iron interface. We compute interstitial and substitutional dopants of different valence and different ionic radius (Ga, B, N, P) to help disambiguate electronic and mechanical effects. B and Ga atoms as substitutional dopants are p-type while N and P atoms lead to n-type doping and all interstitial dopants are n-type. The defect formation energies of all types of dopants are strongly positive (i.e. thermodynamically unfavored), indicating kinetically stabilized systems. Substitutional dopants are strongly energetically preferred to interstitials. In addition, semi-di(tri)-vacancies were investigated. They can be seen as substitutional doping where one dopant replaces two(three) neighbored host atoms. We found that elements like B and N are more stable as substitutional dopants whereas Ga and P are more stable as semi-di-vacancies while no element tested preferred the semi-tri-vacancy configuration. Depending on the element used as dopant, the difference in formation energy between substitutional site and semi-di-vacancy can reach 1 to 4 eV. The effects of dopants on the bulk modulus are not found to be substantial, changing it (vs pure diamond) by within 10%. We therefore also investigate the effects the effects on band alignment at the interface between iron and diamond and thereby on possible electrochemical reactions that might facilitate or inhibit diamond wear.