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KNiH9(CO5)2

High-Entropy Materials HEA

MP-ID: mp-726838 · Space group: P-1 (#2)

Basic Information

Formula
KNiH9(CO5)2
MP-ID
mp-726838
Elements
5
Sites
23
Density
2.2923
g/cm³
Volume
210.71
ų
Cell a
5.3435
Å
Cell b
6.6850
Å
Cell c
6.9947
Å
α Angle
116.23
°
β Angle
89.84
°
γ Angle
107.88
°
Space Group
P-1
Point Group
-1
Crystal System
Triclinic
Bravais Lattice
Triclinic P
Stability
No
Packing Fraction
0.5240

X-ray Diffraction

Diffraction Pattern
X-axis: 2θ (°); Y-axis: relative intensity; CuKa ; λ=1.5406 Å
Diffraction Peaks (Top 24)
2θd (Å)Ihkl
14.29 6.1981 8.3 (0,0,1)
15.59 5.6828 37.8 (0,1,-1)
15.72 5.6377 17.0 (0,1,0)
17.65 5.0236 43.9 (1,0,0)
19.25 4.6115 100.0 (1,-1,0)
20.96 4.2385 58.7 (1,0,-1)
21.12 4.2064 53.3 (1,-1,1)
24.48 3.6358 12.9 (1,0,1)
25.59 3.4809 6.5 (0,1,-2)
25.83 3.4499 11.8 (0,1,1)
26.68 3.3409 3.1 (1,-1,-1)
27.51 3.2418 23.5 (1,1,0)
28.05 3.1810 1.6 (0,2,-1)
28.27 3.1573 67.5 (1,-2,1)
28.81 3.0990 6.2 (0,0,2)
30.63 2.9192 2.0 (1,-2,0)
30.72 2.9102 39.1 (1,-1,2)
31.47 2.8425 19.5 (1,0,-2)
31.49 2.8414 41.9 (0,2,-2)
31.74 2.8189 7.6 (0,2,0)
31.79 2.8145 1.7 (1,1,-2)
32.95 2.7182 4.5 (1,-2,2)
35.65 2.5182 1.0 (1,1,1)
35.75 2.5118 8.9 (2,0,0)
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Energy Properties

Formation Energy/atom
0.43101
eV/atom
Energy/atom
-4.15201
eV/atom
Energy above Hull
1.9493
eV/atom
Uncorrected Energy
-3.7428
eV/atom
Volume/atom
9.16
ų
c/a Ratio
-

Electronic Properties

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

Magnetic Properties

Magnetic
Yes
Total Mag. Moment
2.8297
μB
Mag. Ordering
FM
Mag. Sites
3
Magnetization/Volume
0.013430
μB/ų

Elastic Properties

Elastic data not available

Feature Analysis

Composition Overview

Element Composition (atomic fraction)
Composition Info
Major / Matrix Element
O · 0.435
Element Family
Metalloid-Nonmetal
Solute Fraction
0.565
Interstitial Fraction
0.087

High-Entropy Alloy Features

Composite Radar (normalized)
Element-Class Share
Mix Entropy ΔS/R
1.2143
HEA criterion (>1.0 = high entropy)
Mix Entropy ΔS
10.0958
J/mol·K
Ω Parameter
7.7287
Ω > 1.1 favors solid solution
Atomic Size Mismatch δr
73.541%
δr < 6.6% favors single-phase solid solution
Electronegativity Diff Δχ
0.7202
smaller = more stable mixing
VEC
2.957
valence electron concentration, affects phase stability
Mix Enthalpy ΔH_mix
-0.590
kJ/mol; negative = exothermic mixing
Entropy Norm
0.7545
SS Former
0
Phase Tendency
IM

Related Tasks

Related computation task IDs (2)

Citation & References

Materials Project Page
https://materialsproject.org/materials/mp-726838
Reference Citation

The crystal structure and related material properties of KNiH9(CO5)2 were obtained from the Materials Project database (MP-ID: mp-726838, 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_KNiH9(CO5)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.34345700
_cell_length_b   6.68502865
_cell_length_c   6.99472799
_cell_angle_alpha   116.23073063
_cell_angle_beta   89.83519940
_cell_angle_gamma   107.87549621
_symmetry_Int_Tables_number   1
_chemical_formula_structural   KNiH9(CO5)2
_chemical_formula_sum   'K1 Ni1 H9 C2 O10'
_cell_volume   210.71370025
_cell_formula_units_Z   1
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  0.00000000  0.00000000  0.00000000  1.0
  Ni  Ni1  1  0.50000000  0.50000000  0.50000000  1.0
  H  H2  1  0.35471300  0.00198400  0.87171700  1.0
  H  H3  1  0.64528700  0.99801600  0.12828300  1.0
  H  H4  1  0.41542300  0.40886700  0.75213900  1.0
  H  H5  1  0.58457700  0.59113300  0.24786100  1.0
  H  H6  1  0.00446500  0.17781300  0.58273200  1.0
  H  H7  1  0.99553600  0.82218700  0.41726800  1.0
  H  H8  1  0.19622800  0.00471500  0.60100400  1.0
  H  H9  1  0.80377200  0.99528500  0.39899600  1.0
  H  H10  1  0.00000000  0.50000000  0.00000000  1.0
  C  C11  1  0.62957100  0.71861900  0.79524800  1.0
  C  C12  1  0.37042900  0.28138100  0.20475200  1.0
  O  O13  1  0.45986700  0.25024700  0.76772100  1.0
  O  O14  1  0.54013300  0.74975300  0.23227900  1.0
  O  O15  1  0.13401200  0.25005100  0.50928200  1.0
  O  O16  1  0.86598800  0.74994900  0.49071800  1.0
  O  O17  1  0.71681300  0.03373800  0.70405600  1.0
  O  O18  1  0.28318700  0.96626200  0.29594400  1.0
  O  O19  1  0.39314000  0.66052000  0.74991400  1.0
  O  O20  1  0.60686000  0.33948000  0.25008600  1.0
  O  O21  1  0.80002100  0.43657800  0.94548900  1.0
  O  O22  1  0.19997900  0.56342200  0.05451100  1.0
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