Molecular dynamics investigation of fast Ion transport in Oxide frameworks

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The thesis reports molecular dynamics(MD) investigation of two families of fast ion conductors, namely, Na2M2TeO6, where M=Ni, Zn, Co or Mg, and Li1+xTi2-xAlx(PO4)3, where 0 ? x ? 0.67. These are very promising materials for the development of all-solid-state batteries. Chapter 1 provides a survey of fast ion conduction in various matrices, highlighting complementary knowledge gained through atomistic simulation. Chapter 2 describes the methodology adopted in the present study. Chapter 3 proposes an interatomic-potential-model for Na2M2TeO6, where M=Ni, Zn, Co and Mg, where parameters are determined empirically by fitting to the X-ray structure and ionic conductivity reported previously. This chapter also provides fresh insights on the microscopic mechanism of ion transport in these systems. The potential energies and population profiles of the individual Na+ ions mapped on the basal plane suggests entropic contribution playing a significant role in the Na+ transport at the interlayer. A detailed exploration of the role of ion-ion repulsion was carried out in Chapter 4, wherein interlayers of Na2Ni2TeO6 having different concentrations of the Na+ ions are examined for their individual selfdiffusivity.
Supervisor: Padma Kumar Padmanabhan