We provide a complete quantitative explanation for the anisotropic thermal expansion of hcp Ti at low temperature. The observed negative thermal expansion along the c-axis is reproduced theoretically by means of a parameter free theory which involves both the electron and phonon contributions to the free energy. The thermal expansion of titanium is calculated and found to be negative along the c-axis for temperatures below ∼ 170 K, in good agreement with observations. We have identified a saddle-point Van Hove singularity near the Fermi level as the main reason for the anisotropic thermal expansion in α−titanium.
@article{arxiv.0707.2214,
title = {Anomalous thermal expansion in $\alpha$-titanium},
author = {P. Souvatzis and O. Eriksson and M. I. Katsnelson},
journal= {arXiv preprint arXiv:0707.2214},
year = {2007}
}