Strained Tetragonal States and Bain Paths in Metals

Diplom-Physiker vorgelegt von

We performed total energy calculations on strained tetragonal states of bulk fcc palladium by means of density functional theory using the local density approximation. Coherent epitaxial growth of thin films on cubic (001) substrates results in such strained structures due to heteroepitaxy with mismatch. We obtained what is called the epitaxial Bain path of palladium, a structural transition be...

Theoretical Studies of Epitaxial Bain Paths of Metals

Tetragonal states from epitaxial strain on metal films

The tetragonal states produced by isotropic pseudomorphic epitaxial strain in the ~001! plane on a tetragonal phase of a crystal are calculated for V, Ti, Rb, Li, K, and Sr from first-principles electronic theory. It is shown that each metal has two tetragonal phases corresponding to minima of the total energy with respect to tetragonal deformations ~and hence are equilibrium phases! and that t...

Computer study of the bcc fcc structure change by homogeneous deformations

The Bain transformation bcc ~ fcc can be achieved by the two homogeneous « shears » E and E’ proposed by Bogers and Burgers. We first discuss the conditions for pair potentials to ensure the mechanical stability of both bcc and fcc structures; then, three phenomenological potentials for metals are used to calculate the crystal free energy density W for the deformation states 03B3E + 03B3’ E’ (0...

Optimality of general lattice transformations with applications to the Bain strain in steel.

This article provides a rigorous proof of a conjecture by E. C. Bain in 1924 on the optimality of the so-called Bain strain based on a criterion of least atomic movement. A general framework that explores several such optimality criteria is introduced and employed to show the existence of optimal transformations between any two Bravais lattices. A precise algorithm and a graphical user interfac...