Gunnar K. Palsson, Moritz Wälde, Martin Amft, Yuanyuan Wu, Martina Ahlberg, Max Wolff, Björgvin Hjörvarsson
The dipole force components in nano-sized metal hydrides are quantitatively determined with curvature and x-ray diffraction measurements. Ab-initio density functional theory is used to calculate the dipole components and the symmetry of the strain field. The hydrogen occupancy in a 100 nm thick V film is shown to be tetrahedral with a slight asymmetry at low concentration and a transition to octahedral occupancy is shown to take place at around 0.07 [H/V] at 360 K. When the thickness of the V layer is reduced to 3 nm and biaxially strained, in a Fe$_{0.5}$V$_{0.5}$/V superlattice, the hydrogen unequivocally occupies octahedral $z$-like sites, even at and below concentrations of 0.02 [H/V].
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http://arxiv.org/abs/1203.4247
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