Place: Thomas Young Centre Soiree, King’s College, London, UK
Albeit quantum mechanics provides a fundamental and highly accurate basis for materials science, quantum mechanics is rarely used as the basis for the development of a new material. This is due to the hierarchical structure of materials, where several orders in length and time need to be bridged between the electronic structure and the mechanical behaviour on the component scale.
The Interdisciplinary Centre for Advanced Materials Simulation (ICAMS) was set up two years ago with the aim of supporting the development and improvement of materials with modelling and simulation starting from a quantum mechanical description of materials. ICAMS is supported by a consortium that comprises companies from steel and chemical industry. One of the core projects at ICAMS is the derivation of classical, effective interatomic interactions from a quantum mechanical treatment of bond formation.
Following Pettifor, the electronic structure is coarse-grained at two levels of approximation. In a first step, the description of the electronic structure is simplified to the tight-binding approximation. In a second step, a moments expansion of the tight-binding Hamiltonian results in a classical, effective interatomic interaction, the analytic bond-order potential (BOP). The format of the potential includes charge transfer and magnetic contributions to the binding energy. The BOP reproduces the structural trend across the non-magnetic 4d and 5d TM series and displays the experimental trend from anti-ferromagnetic order to ferromagnetic order across the 3d transition metal series. For iron, the potential correctly predicts a large magnetic energy for the alpha phase whereas the close-packed gamma and epsilon phases exhibit only a small magnetic contribution to the binding energy.