  Equation of state (EOS) for bcc tungsten at 300 K (or 3000 K) up to 1000 GPa
(or 300 GPa) was predicted for the first time by solving the partition function
via a direct integral approach (DIA) with ab initio calculations of the atoms'
interactions. Compared with available experiments under static compressions up
to 150 GPa (or 35 GPa) for room temperature (or 1673 K), all the calculated
results are within the experimental uncertainty achieved very recently.
Furthermore, the same procedure was performed to investigate the shock wave
experiments on the EOS up to 400 GPa and 10000 K, and the calculated average
pressure deviates the experimental measurements by only 2.0%. These facts
suggest that the other calculated results of DIA for the EOS are reliable, and
DIA as a universal method without any artificial parameters could be widely
applied to predict EOS of various materials under various conditions.
