Electronic structure of metal hydrides. IV.<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">Ti</mml:mi><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">Zr</mml:mi><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">Hf</mml:mi><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>, and the fcc-fct lattice distortion

Abstract

The electronic structures of $\mathrm{Ti}{\mathrm{H}}_{x}$, $\mathrm{Zr}{\mathrm{H}}_{x}$, and $\mathrm{Hf}{\mathrm{H}}_{x}$ have been studied using photoelectron spectroscopy and synchrotron radiation. Structures in the metal $d$-derived band within \ensuremath{\sim}3 eV of the Fermi level ${E}_{F}$ and in the bonding band (\ensuremath{\sim}3-10 eV below ${E}_{F}$) are compared with theory. In each dihydride, the bonding band center falls at -5.5 eV, at approximately the same energy as previously observed for the dihydrides of Sc and Y. Changes in the emission features near ${E}_{F}$ and at -7 eV have been observed in samples bridging the $\mathrm{fcc}\ensuremath{\rightarrow}\mathrm{fct}$ distortion in $\mathrm{Zr}{\mathrm{H}}_{x}$, $1.63\ensuremath{\le}x\ensuremath{\le}1.94$. The changes at ${E}_{F}$ demonstrate the Jahn-Teller effect for the electronic states of $\mathrm{Zr}{\mathrm{H}}_{x}$. The binding energies of the Ti $3p$, Zr $4p$, Hf $5p$, and Hf $4f$ cores are observed to be greater than in the elemental metals, consistent with charge transfer to the hydrogen site.