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KCoO2

High-Entropy Materials HEA Traditional Materials TRA

MP-ID: mp-557137 · Space group: I-4 (#82)

Basic Information

Formula
KCoO2
MP-ID
mp-557137
Elements
3
Sites
8
Density
3.7998
g/cm³
Volume
113.65
ų
Cell a
5.3231
Å
Cell b
5.3217
Å
Cell c
5.3243
Å
α Angle
99.72
°
β Angle
114.56
°
γ Angle
114.55
°
Space Group
I-4
Point Group
-4
Crystal System
Tetragonal
Bravais Lattice
Tetragonal I
Stability
No
Packing Fraction
0.7400

X-ray Diffraction

Diffraction Pattern
X-axis: 2θ (°); Y-axis: relative intensity; CuKa ; λ=1.5406 Å
Diffraction Peaks (Top 24)
2θd (Å)Ihkl
20.13 4.4105 25.3 (1,0,-1)
20.13 4.4105 25.2 (0,0,1)
20.14 4.4091 25.2 (1,-1,0)
20.14 4.4089 25.1 (0,1,0)
25.97 3.4314 2.9 (1,-1,-1)
31.08 2.8776 88.4 (1,-1,1)
31.08 2.8775 88.5 (1,1,-1)
34.17 2.6239 99.9 (1,0,-2)
34.18 2.6233 99.9 (2,-1,-1)
34.18 2.6232 100.0 (0,1,1)
34.19 2.6226 99.9 (1,-2,0)
37.31 2.4102 2.4 (0,1,-2)
37.31 2.4102 2.2 (1,1,-2)
37.31 2.4100 2.4 (2,0,-1)
37.31 2.4100 2.2 (1,0,1)
37.32 2.4098 2.2 (2,-1,0)
37.32 2.4097 2.5 (1,1,0)
37.32 2.4095 2.5 (1,-2,1)
37.32 2.4095 2.2 (0,2,-1)
40.92 2.2053 1.3 (2,0,-2)
40.92 2.2052 1.3 (0,0,2)
40.94 2.2045 1.3 (2,-2,0)
40.94 2.2045 1.3 (0,2,0)
44.53 2.0347 44.1 (2,0,0)
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Energy Properties

Formation Energy/atom
-1.47961
eV/atom
Energy/atom
-6.01978
eV/atom
Energy above Hull
0.0246
eV/atom
Uncorrected Energy
-5.2668
eV/atom
Volume/atom
14.21
ų
c/a Ratio
1.0002

Electronic Properties

Metallic
Metal
Band Gap
0
eV
Direct Gap
No
CBM
N/A
eV

Magnetic Properties

Magnetic
Yes
Total Mag. Moment
6.0056
μB
Mag. Ordering
Unknown
Mag. Sites
0
Magnetization/Volume
0.052840
μB/ų

Elastic Properties

Elastic data not available

Feature Analysis

Composition Overview

Element Composition (atomic fraction)
Composition Info
Major / Matrix Element
O · 0.500
Element Family
Metalloid-Nonmetal
Solute Fraction
0.500
Interstitial Fraction
0.000

High-Entropy Alloy Features

Composite Radar (normalized)
Element-Class Share
Mix Entropy ΔS/R
1.0397
HEA criterion (>1.0 = high entropy)
Mix Entropy ΔS
8.6442
J/mol·K
Ω Parameter
0.0000
Ω > 1.1 favors solid solution
Atomic Size Mismatch δr
56.357%
δr < 6.6% favors single-phase solid solution
Electronegativity Diff Δχ
1.1102
smaller = more stable mixing
VEC
4.500
valence electron concentration, affects phase stability
Mix Enthalpy ΔH_mix
0.000
kJ/mol; negative = exothermic mixing
Entropy Norm
0.9464
SS Former
0
Phase Tendency
IM

Traditional Material Features

ROM Blended-Feature Radar
Rating & Classification
Tier
B
Score
0.452
Family
O-rich Multi-Component
Matrix Element
O · 0.500

Related Tasks

Citation & References

Materials Project Page
https://materialsproject.org/materials/mp-557137
Reference Citation

The crystal structure and related material properties of KCoO2 were obtained from the Materials Project database (MP-ID: mp-557137, database version v2026.04.13).

Literature Citation

Horton, M.K., Huck, P., Yang, R.X. et al. Accelerated data-driven materials science with the Materials Project. Nat. Mater. 24, 1522–1532 (2025). https://doi.org/10.1038/s41563-025-02272-0

BibTeX
@article{Horton2025,
  author  = {Horton, Matthew K. and Huck, Patrick and Yang, Ruo Xi and Munro, Jason M. and Dwaraknath, Shyam and Ganose, Alex M. and Kingsbury, Ryan S. and Wen, Mingjian and Shen, Jimmy X. and Mathis, Tyler S. and Kaplan, Aaron D. and Berket, Karlo and Riebesell, Janosh and George, Janine and Rosen, Andrew S. and Spotte-Smith, Evan W. C. and McDermott, Matthew J. and Cohen, Orion A. and Dunn, Alex and Kuner, Matthew C. and Rignanese, Gian-Marco and Petretto, Guido and Waroquiers, David and Griffin, Sinead M. and Neaton, Jeffrey B. and Chrzan, Daryl C. and Asta, Mark and Hautier, Geoffroy and Cholia, Shreyas and Ceder, Gerbrand and Ong, Shyue Ping and Jain, Anubhav and Persson, Kristin A.},
  title   = {Accelerated data-driven materials science with the Materials Project},
  journal = {Nature Materials},
  year    = {2025},
  volume  = {24},
  number  = {10},
  pages   = {1522--1532},
  month   = {oct},
  doi     = {10.1038/s41563-025-02272-0},
  issn    = {1476-4660},
  url     = {https://doi.org/10.1038/s41563-025-02272-0},
  abstract = {The Materials Project was launched formally in 2011 to drive materials discovery forwards through high-throughput computation and open data. More than a decade later, the Materials Project has become an indispensable tool used by more than 600,000 materials researchers around the world. This Perspective describes how the Materials Project, as a data platform and a software ecosystem, has helped to shape research in data-driven materials science. We cover how sustainable software and computational methods have accelerated materials design while becoming more open source and collaborative in nature. Next, we present cases where the Materials Project was used to understand and discover functional materials. We then describe our efforts to meet the needs of an expanding user base, through technical infrastructure updates ranging from data architecture and cloud resources to interactive web applications. Finally, we discuss opportunities to better aid the research community, with the vision that more accessible and easy-to-understand materials data will result in democratized materials knowledge and an increasingly collaborative community.}
}

3D Crystal Structure Rendering

Loading 3D structure…

Style: Ball & Stick
Raw CIF Data
# generated using pymatgen
data_KCoO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.32310896
_cell_length_b   5.32173345
_cell_length_c   5.32432251
_cell_angle_alpha   99.72468896
_cell_angle_beta   114.56187482
_cell_angle_gamma   114.54595294
_symmetry_Int_Tables_number   1
_chemical_formula_structural   KCoO2
_chemical_formula_sum   'K2 Co2 O4'
_cell_volume   113.64979325
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  K  K0  1  0.50002800  0.25001523  0.75001480  1.0
  K  K1  1  -0.00001181  0.50001085  0.49997727  1.0
  Co  Co2  1  0.50007689  0.74986872  0.25016530  1.0
  Co  Co3  1  0.00037132  0.00014456  0.00026162  1.0
  O  O4  1  0.85910128  0.82972660  0.22319451  1.0
  O  O5  1  0.14051944  0.36395767  0.97007864  1.0
  O  O6  1  0.39358666  0.02966865  0.17039679  1.0
  O  O7  1  0.60632922  0.77660971  0.63591407  1.0
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