The vibration-rotation states of a tetrahedral molecule in a field of D3h symmetry are studied by an extended group theory. Symmetry adapted rotational wave functions for the ground and the triply degenerate excited vibrational states are constructed. The crystal field potential is derived explicitly for a tetrahedral molecule in a hexagonal close-packed crystal. As an example, the rovibrationa...

Materials with a hexagonal close-packed (hcp) crystal structure such as Mg, Ti and Zr are being used in the transportation, aerospace and nuclear industry, respectively. Material strength and formability are critical qualities for shaping these materials into parts and a pervasive deformation mechanism that significantly affects their formability is deformation twinning. The interaction between...

We have investigated twin boundaries in double-lattice hexagonal close-packed metallic materials, focusing on their atomic geometry. Combining accurate ab-initio methods and large-scale atomistic simulations we address the following two fundamental questions: (i) What are the possible intrinsic twin boundary structures in hcp crystals? (ii) Are these structures stable against small distortions?...

We report here the compositional dependency of face-centered cubic (FCC) to hexagonal close-packed (HCP) martensitic transformation in FeMnCo medium entropy alloys (MEAs) and insights into underlying mechanisms. To this end, we designed MEAs with same Fe-to-Mn ratio explored phase stability therein. Higher Co content was found facilitate FCC-HCP kinetics. In situ electron backscatter diffractio...

Analytical formulae are derived for the zero-point vibrational energy and anharmonicity corrections of cohesive mode Gr\"{u}neisen parameter within Einstein model cubic lattices (sc, bcc fcc) hexagonal close-packed structure. This extends work done by Lennard Jones Ingham in 1924, Corner 1939 Wallace 1965. The based on description two-body contributions an inverse power expansion (extended Lenn...