Thermodynamics of metal nanoparticles: Energies and enthalpies of formation of magnesium clusters and nanoparticles as large as 1.3 nm

The major obstacle that prevents reliable electronic structure studies of nanoparticles is the rapid increasing computational cost for benchmark calculations using coupled-cluster methods. We show that a CCSD(T) scheme with an MP2/CBS correction can reproduce accurate cohesive energies for magnesium clusters, and this scheme is much less computationally demanding than other reliable methods, so it is applied to Mgn with n up to 19, which enters the realm of nanoparticles. (The diameters of all Mg clusters n = 11 are >1 nm). With the extended benchmark data, we validate exchange-correlation functionals into the nanoparticle regime and use the two bestvalidated functionals to calculate the enthalpy of formation of Mg28, with a diameter of 1.30 nm. We also calculated the enthalpy of formation of all Mg clusters and nanoparticles from Mg2 to Mg19. This kind of reliable thermodynamic data on size-selected metal nanoparticles has been hard to come by, either experimentally or theoretically, but it is badly needed to support applications in catalysis, electrochemistry, and other technologies.