To read the json.bz2 files you can use the following code in python:

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#!/usr/bin/env python

import json, bz2
from pymatgen.entries.computed_entries import ComputedStructureEntry

with bz2.open("dcgat_1_000.json.bz2") as fh:
  data = json.loads(fh.read().decode('utf-8'))

entries = [ComputedStructureEntry.from_dict(i) for i in data["entries"]]

print("Found " + str(len(entries)) + " entries")
print("\nEntry:\n", entries[0])
print("\nStructure:\n", entries[0].structure)

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Output:

Found 100000 entries

Entry: None ComputedStructureEntry - Hf2 Mg1 Ga1 Cl1 (Hf2MgGaCl)
Energy (Uncorrected)     = -21.2544  eV (-4.2509  eV/atom)
Correction               = 0.0000    eV (0.0000   eV/atom)
Energy (Final)           = -21.2544  eV (-4.2509  eV/atom)
Energy Adjustments:
  None
Parameters:
Data:
  mat_id                 = agm001459480
  prototype_id           = ABCD2_2_spg123
  location               = cgat_prot/ABCD2_prot2_spg123/runs/batch-004/Mg/MgClGaHf2/xxx_02p-00_agm001459480_spg123
  formula                = Hf2MgGaCl
  elements               = ['Mg', 'Hf', 'Ga', 'Cl']
  spg                    = 123
  nsites                 = 5
  stress                 = [[1.7837616, 0.0, 0.0], [0.0, -0.5098393, 0.0], [0.0, 0.0, 1.7837616]]
  energy_total           = -21.25442493
  total_mag              = -1e-07
  band_gap_ind           = 0.0153
  band_gap_dir           = 0.0709
  dos_ef                 = 6.71315
  energy_corrected       = -21.254425
  e_above_hull           = 1.827256
  e_form                 = 0.90605843
  e_phase_separation     = 1.827256
  decomposition          =  Mg149Ga  Hf2Ga  MgCl2  Hf 

Structure: Full Formula (Hf2 Mg1 Ga1 Cl1)
Reduced Formula: Hf2MgGaCl
abc   :   5.325481   4.458459   5.325481
angles:  90.000000  90.000000  90.000000
Sites (5)
  #  SP      a    b    c    charge  forces             magmom
---  ----  ---  ---  ---  --------  ---------------  --------
  0  Mg    0    0    0       6.473  [0.0, 0.0, 0.0]        -0
  1  Hf    0    0    0.5     7.872  [0.0, 0.0, 0.0]         0
  2  Hf    0.5  0    0       7.946  [0.0, 0.0, 0.0]        -0
  3  Ga    0.5  0.5  0.5    11.436  [0.0, 0.0, 0.0]         0
  4  Cl    0    0.5  0       5.141  [0.0, 0.0, 0.0]        -0

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List of POTCARs used:

Ac: PAW_PBE Ac 06Sep2000
Ag: PAW_PBE Ag 06Sep2000
Al: PAW_PBE Al 04Jan2001
As: PAW_PBE As 06Sep2000
Au: PAW_PBE Au 06Sep2000
B: PAW_PBE B 06Sep2000
Ba: PAW_PBE Ba_sv 06Sep2000
Be: PAW_PBE Be_sv 06Sep2000
Bi: PAW_PBE Bi 08Apr2002
Br: PAW_PBE Br 06Sep2000
C: PAW_PBE C 08Apr2002
Ca: PAW_PBE Ca_sv 06Sep2000
Cd: PAW_PBE Cd 06Sep2000
Ce: PAW_PBE Ce 28Sep2000
Cl: PAW_PBE Cl 17Jan2003
Co: PAW_PBE Co 06Sep2000
Cr: PAW_PBE Cr_pv 07Sep2000
Cs: PAW_PBE Cs_sv 08Apr2002
Cu: PAW_PBE Cu_pv 06Sep2000
Dy: PAW_PBE Dy_3 06Sep2000
Er: PAW_PBE Er_3 06Sep2000
Eu: PAW_PBE Eu 08Apr2002
F: PAW_PBE F 08Apr2002
Fe: PAW_PBE Fe_pv 06Sep2000
Ga: PAW_PBE Ga_d 06Sep2000
Gd: PAW_PBE Gd 08Apr2002
Ge: PAW_PBE Ge_d 06Sep2000
H: PAW_PBE H 15Jun2001
Hf: PAW_PBE Hf_pv 06Sep2000
Hg: PAW_PBE Hg 06Sep2000
Ho: PAW_PBE Ho_3 06Sep2000
I: PAW_PBE I 08Apr2002
In: PAW_PBE In_d 06Sep2000
Ir: PAW_PBE Ir 06Sep2000
K: PAW_PBE K_sv 06Sep2000
La: PAW_PBE La 06Sep2000
Li: PAW_PBE Li_sv 23Jan2001
Lu: PAW_PBE Lu_3 06Sep2000
Mg: PAW_PBE Mg_pv 06Sep2000
Mn: PAW_PBE Mn_pv 07Sep2000
Mo: PAW_PBE Mo_pv 08Apr2002
N: PAW_PBE N 08Apr2002
Na: PAW_PBE Na_pv 05Jan2001
Nb: PAW_PBE Nb_pv 08Apr2002
Nd: PAW_PBE Nd_3 06Sep2000
Ni: PAW_PBE Ni_pv 06Sep2000
Np: PAW_PBE Np 06Sep2000
O: PAW_PBE O 08Apr2002
Os: PAW_PBE Os_pv 20Jan2003
P: PAW_PBE P 17Jan2003
Pa: PAW_PBE Pa 07Sep2000
Pb: PAW_PBE Pb_d 06Sep2000
Pd: PAW_PBE Pd 05Jan2001
Pm: PAW_PBE Pm_3 07Sep2000
Pr: PAW_PBE Pr_3 07Sep2000
Pt: PAW_PBE Pt 05Jan2001
Pu: PAW_PBE Pu 06Sep2000
Rb: PAW_PBE Rb_sv 06Sep2000
Re: PAW_PBE Re_pv 06Sep2000
Rh: PAW_PBE Rh_pv 06Sep2000
Ru: PAW_PBE Ru_pv 06Sep2000
S: PAW_PBE S 17Jan2003
Sb: PAW_PBE Sb 06Sep2000
Sc: PAW_PBE Sc_sv 07Sep2000
Se: PAW_PBE Se 06Sep2000
Si: PAW_PBE Si 05Jan2001
Sm: PAW_PBE Sm_3 07Sep2000
Sn: PAW_PBE Sn_d 06Sep2000
Sr: PAW_PBE Sr_sv 07Sep2000
Ta: PAW_PBE Ta_pv 07Sep2000
Tb: PAW_PBE Tb_3 06Sep2000
Tc: PAW_PBE Tc_pv 06Sep2000
Te: PAW_PBE Te 08Apr2002
Th: PAW_PBE Th 07Sep2000
Ti: PAW_PBE Ti_pv 07Sep2000
Tl: PAW_PBE Tl_d 06Sep2000
Tm: PAW_PBE Tm_3 20Jan2003
U: PAW_PBE U 06Sep2000
V: PAW_PBE V_sv 07Sep2000
W: PAW_PBE W_pv 06Sep2000
Y: PAW_PBE Y_sv 06Sep2000
Yb: PAW_PBE Yb 24Feb2003
Zn: PAW_PBE Zn 06Sep2000
Zr: PAW_PBE Zr_sv 07Sep2000