CaAc(Si2Ir3)2

High-Entropy Materials HEA

MP-ID: mp-3251820 · Space group: Imm2 (#44)

Materials Project API

Basic Information

Formula

CaAc(Si2Ir3)2

MP-ID

mp-3251820

Elements

Sites

Density

12.7121

g/cm³

Volume

200.21

Å³

Cell a

6.7194

Cell b

6.7165

Cell c

6.7199

α Angle

130.05

β Angle

115.57

γ Angle

85.67

Space Group

Imm2

Point Group

mm2

Crystal System

Orthorhombic

Bravais Lattice

Stability

Yes

Packing Fraction

X-ray Diffraction

Diffraction Pattern

Target / Radiation

X-axis: 2θ (°); Y-axis: relative intensity; Cu Kα ; λ=1.5418 Å

Diffraction Peaks (Top 24)

2θ	d (Å)	I	hkl
15.29	5.7952	15.1	(1,0,0)
15.29	5.7934	15.1	(0,1,-1)
18.01	4.9263	10.4	(1,1,-1)
18.04	4.9169	9.5	(1,0,-1)
18.05	4.9156	9.5	(0,1,0)
19.96	4.4490	11.2	(0,0,1)
19.97	4.4459	11.1	(1,-1,0)
24.86	3.5821	70.6	(1,-1,1)
27.00	3.3019	4.3	(1,1,-2)
27.01	3.3018	4.3	(1,1,0)
27.01	3.3013	4.3	(2,0,-1)
27.02	3.2998	4.3	(0,2,-1)
29.93	2.9858	3.8	(2,1,-1)
29.93	2.9851	3.8	(1,2,-2)
30.86	2.8976	23.5	(2,0,0)
30.87	2.8967	23.5	(0,2,-2)
30.88	2.8961	29.0	(1,0,1)
30.88	2.8959	29.0	(0,1,-2)
30.89	2.8946	29.0	(2,-1,0)
30.90	2.8939	29.0	(1,-2,1)
35.22	2.5483	2.8	(1,0,-2)
35.22	2.5481	2.8	(0,1,1)
35.23	2.5473	2.8	(2,-1,-1)
35.24	2.5467	2.8	(1,-2,0)

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Energy Properties

Formation Energy/atom

-0.94572

eV/atom

Energy/atom

-36.35630

eV/atom

Energy above Hull

0.0000

eV/atom

Uncorrected Energy

-36.3563

eV/atom

Volume/atom

16.68

Å³

c/a Ratio

1.0001

Electronic Properties

Metallic

Metal

Band Gap

Direct Gap

CBM

N/A

Magnetic Properties

Magnetic

Total Mag. Moment

0.0000

μB

Mag. Ordering

Mag. Sites

Magnetization/Volume

0.000000

μB/Å³

Elastic Properties

Elastic data not available

Feature Analysis

Composition Overview

Element Composition (atomic fraction)

Composition Info

Major / Matrix Element

Ir · 0.500

Element Family

5d-TM

Solute Fraction

0.500

Interstitial Fraction

0.333

High-Entropy Alloy Features

Composite Radar (normalized)

Element-Class Share

Mix Entropy ΔS/R

1.1269

HEA criterion (>1.0 = high entropy)

Mix Entropy ΔS

9.3693

J/mol·K

Ω Parameter

1.1747

Ω > 1.1 favors solid solution

Atomic Size Mismatch δr

19.039%

δr < 6.6% favors single-phase solid solution

Electronegativity Diff Δχ

0.4071

smaller = more stable mixing

VEC

6.167

valence electron concentration, affects phase stability

Mix Enthalpy ΔH_mix

-17.029

kJ/mol; negative = exothermic mixing

Entropy Norm

0.8129

SS Former

Phase Tendency

Related Tasks

Related computation task IDs (1)

aaahdaka

Citation & References

Materials Project Page

https://materialsproject.org/materials/mp-3251820

Reference Citation

The crystal structure and related material properties of CaAc(Si2Ir3)2 were obtained from the Materials Project database (MP-ID: mp-3251820, 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

3D Crystal Structure Rendering

Loading 3D structure…

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Raw CIF Data

# generated using pymatgen
data_CaAc(Si2Ir3)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.71943618
_cell_length_b   6.71646855
_cell_length_c   6.71988970
_cell_angle_alpha   130.05244344
_cell_angle_beta   115.57254414
_cell_angle_gamma   85.67141301
_symmetry_Int_Tables_number   1
_chemical_formula_structural   CaAc(Si2Ir3)2
_chemical_formula_sum   'Ca1 Ac1 Si4 Ir6'
_cell_volume   200.21410113
_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
  Ca  Ca0  1  0.74998723  0.03317712  0.28336031  1.0
  Ac  Ac1  1  0.25025405  0.97833561  0.72850122  1.0
  Si  Si2  1  0.07021562  0.27167688  0.20137766  1.0
  Si  Si3  1  0.91214224  0.70691939  0.79473452  1.0
  Si  Si4  1  0.42960388  0.63056554  0.20086503  1.0
  Si  Si5  1  0.58770291  0.38338790  0.79552618  1.0
  Ir  Ir6  1  0.49252783  0.50269648  0.49517016  1.0
  Ir  Ir7  1  0.00765837  0.50274981  0.01041826  1.0
  Ir  Ir8  1  0.28284461  0.00022828  0.27805168  1.0
  Ir  Ir9  1  0.72245178  0.00011383  0.71714445  1.0
  Ir  Ir10  1  0.21681818  0.49472327  0.71705129  1.0
  Ir  Ir11  1  0.77779331  0.49542889  0.27779923  1.0

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