Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Thermal contributions to the structural phase transitions of crystalline
  aluminum under ultrahigh pressures   The \emph{ab initio} computations of thermodynamic properties of condensed
matters under extreme conditions is a long-time pursuit. In this work, the
pressure induced structural phase transitions of crystalline aluminum up to
$600$ GPa at room temperature is investigated by the criterion of free energy
derived directly from the partition function formulated in ensemble theory with
the interatomic interactions characterized by density functional theory
computations. The transition pressures of the
FCC$\rightarrow$HCP$\rightarrow$BCC phase transition are determined at $194$
and $361$ GPa, the axial ratio of the HCP structure is found to be equal to
$1.62$ and the discontinuities in the equations of states are confirmed to be
associated with $-0.674\%$ and $-0.897\%$ volume changes, which all validate
the accuracy of measurements by one of the recent experiments but disagree with
the results by others. Compared with the results obtained by the widely used
criterion of enthalpy at $0$K, this work shows that the thermal contributions
play a nontrivial role for the structural stability of aluminum even under a
room-temperature circumstance.

2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph
20
The categories of this paper are: acc-phys
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
23
The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio
29
The categories of this paper are: funct-an