Solid He is studied in the pressure and temperature ranges 1–40 TPa and 0–10,000 K using first-principles methods .
Anharmonic vibrational properties are calculated within a self-consistent field framework , including the internal and free energies , density-pressure relation , stress tensor , thermal expansion , and the electron-phonon coupling renormalization of the electronic band gap .
We find that an accurate description of electron-phonon coupling requires us to use a non-perturbative approach .
The metalization pressure of 32.9 TPa at 0 K is larger than found previously .
The vibrational effects are large ; for example at P = 30 TPa the band gap is increased by 2.8 eV by electron-phonon coupling and a further 0.1 eV by thermal expansion compared to the static value .
The implications of the calculated metalization pressure for the cooling of white dwarfs are discussed .