The root cause of hydrogen induced changes in optical transmission of vanadium

TL;DR

This paper investigates how hydrogen absorption causes changes in the optical transmission of vanadium layers, revealing that volume expansion, rather than hydrogen concentration, is the primary factor, supported by experiments and first-principles calculations.

Contribution

It demonstrates that hydrogen-induced optical changes in vanadium are mainly due to volume expansion, using superlattice experiments and density functional theory for validation.

Findings

Optical transmission changes are dominated by volume expansion.

Hydrogen resides in vanadium layers at different sites, causing varying lattice expansion.

Experimental results agree with first-principles density functional calculations.

Abstract

The changes in the optical transmission of thin vanadium layers upon hydrogen absorption are found to be dominated by the volume changes of the layers and not directly linked to concentration. This effect is demonstrated by utilising the difference in the hydrogen induced expansion of V layers in Fe/V and Cr/V superlattices. Hydrogen resides solely in the vanadium layers in these superlattices, while occupying different sites, causing different lattice expansion. Quantitative agreement is obtained between the experimental results and first principle density functional calculations.