Theoretical studies of thermodynamic properties of clusters at low temperatures

• Applicant: Professor Dr. Michael Springborg
• Subject Area: Theoretical Chemistry: Molecules, Materials, Surfaces
• Term: from 2007 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 34425465

Two existing computer program packages, i.e., an embedded atom method and a parameterized density-functional method, shall be so extended that more energetically lowest isomers of clusters can be determined, and so that vibrational properties, withín a harmonic approximation, can be determined. Subsequently, the partition function shall be calculated and from this various thermodynamic quantities, like entropy, free energy, and heat capacity as a function of cluster size and temperature, shall be determined. The methods shall be applied on different systems, i.e., NaN, CuN, AuN, AlN and Ni-Cu clusters and the results shall be used in addressing the following questions: Does temperature via entropy effects lead to changes in the magic numbers? Does temperature lead to changes in the relative total energies of different isomers of the same cluster size? How important is the co-existence of more different energetically close isomers for the properties of the clusters? Can the ‘magic numbers’ be seen in heat capacities, i.e., are the magic clusters particularly rigid and have, therefore, particularly low heat capacities? How important are electronic degrees of freedom for the thermodynamic quantities, i.e., since electronic excitation energies most often are much larger than kT, one may expect the electrons to be irrelevant for the thermodynamic quantities? At which level of approximation does one get an adequate description of the thermodynamic properties of the clusters as a function of temperature and size?

• DFG Programme: Research Grants