Experimental dimer-monomer ³He NMR shift inside C₆₀ explained from first principles by Path Integral Monte Carlo modelling

Abstract. In my thesis I simulate the endohedral fullerene molecules of helium monomer He1@C60 and dimer He2@C60 and the corresponding hexa-anions, with the intention of determining the chemical shift of the helium. Different models are considered, including cavity models where the presence of fullerene is described by spherically symmetric fields acting on the helium atoms, rigid models where the carbon atoms remain fixed, and dynamic models where all the atoms are moving. The simulations are implemented as path integral Monte Carlo (PIMC) code where the discretization of the path integrals (Trotter number) can be specified independently for helium and carbon atoms. The PIMC approach gives a correction to the position distributions of both helium and carbon atoms, and it is shown that both the Trotter numbers of helium and carbon influence the chemical shifts