We study the magnetic properties of platinum diselenide (PtSe2) intercalated with Ti, V, Cr, and Mn, using first-principle density functional theory (DFT) calculations and Monte Carlo (MC) simulations. First, we present the equilibrium position of intercalants in PtSe2 obtained from the DFT calculations. Next, we present the magnetic groundstates for each of the intercalants in PtSe2 along with their critical temperature. We show that Ti intercalants result in an in-plane AFM and out-of-plane FM groundstate, whereas Mn intercalant results in in-plane FM and out-of-plane AFM. V intercalants result in an FM groundstate both in the in-plane and the out-of-plane direction, whereas Cr results in an AFM groundstate both in the in-plane and the out-of-plane direction. We find a critical temperature of <0.01 K, 111 K, 133 K, and 68 K for Ti, V, Cr, and Mn intercalants at a 7.5% intercalation, respectively. In the presence of Pt vacancies, we obtain critical temperatures of 63 K, 32 K, 221 K, and 45 K for Ti, V, Cr, and Mn-intercalated PtSe2, respectively. We show that Pt vacancies can change the magnetic groundstate as well as the critical temperature of intercalated PtSe2, suggesting that the magnetic groundstate in intercalated PtSe2 can be controlled via defect engineering.
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Effect of Nitrogen Doping and Oxidation of Graphene on the Deposition of Platinum from Trimethyl(methylcyclopentadienyl)platinum(IV)
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While it is well established that nanoparticle shape can depend on equilibrium thermodynamics or growth kinetics, recent computational work has suggested the importance of thermal energy in controlling the distribution of shapes in populations of nanoparticles. Here, we used transmission electron microscopy to characterize the shapes of bare platinum nanoparticles and observed a strong dependence of shape distribution on particle size. Specifically, the smallest nanoparticles (<2.5 nm) had a truncated octahedral shape, bound by 〈111〉 and 〈100〉 facets, as predicted by lowest-energy thermodynamics. However, as particle size increased, the higher-energy 〈110〉 facets became increasingly common, leading to a large population of non-equilibrium truncated cuboctahedra. The observed trends were explained by combining atomistic simulations (both molecular dynamics and an empirical square-root bond-cutting model) with Boltzmann statistics. Overall, this study demonstrates experimentally how thermal energy leads to shape variation in populations of metal nanoparticles, and reveals the dependence of shape distributions on particle size. The prevalence of non-equilibrium facets has implications for metal nanoparticles applications from catalysis to solar energy.more » « less