Pa2Al9Ir2Os

High-Entropy Materials HEA

MP-ID: mp-3292807 · Space group: Cmcm (#63)

Materials Project API

Basic Information

Formula

Pa2Al9Ir2Os

MP-ID

mp-3292807

Elements

Sites

Density

9.1241

g/cm³

Volume

465.75

Å³

Cell a

7.5719

Cell b

7.5718

Cell c

9.2824

α Angle

90.00

β Angle

90.00

γ Angle

118.94

Space Group

Cmcm

Point Group

mmm

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
13.36	6.6266	9.7	(1,0,-1,0)
13.36	6.6266	9.8	(0,1,-1,0)
13.58	6.5220	14.7	(1,-1,0,0)
16.44	5.3933	23.3	(1,0,-1,1)
16.44	5.3933	23.3	(0,1,-1,1)
19.12	4.6412	6.4	(0,0,0,2)
23.12	3.8467	21.6	(1,1,-2,0)
23.40	3.8015	4.8	(1,0,-1,2)
23.40	3.8015	4.8	(0,1,-1,2)
23.50	3.7853	14.7	(2,-1,-1,0)
23.50	3.7853	14.7	(1,-2,1,0)
23.53	3.7814	4.4	(1,-1,0,2)
25.06	3.5536	42.0	(1,1,-2,1)
25.41	3.5051	32.7	(2,-1,-1,1)
25.41	3.5050	32.7	(1,-2,1,1)
27.35	3.2610	11.1	(2,-2,0,0)
28.61	3.1205	6.0	(2,0,-2,1)
28.61	3.1205	6.0	(0,2,-2,1)
30.18	2.9617	85.5	(1,1,-2,2)
30.47	2.9334	100.0	(2,-1,-1,2)
30.47	2.9334	100.0	(1,-2,1,2)
31.92	2.8036	6.4	(1,0,-1,3)
31.92	2.8036	6.4	(0,1,-1,3)
33.22	2.6967	1.8	(2,0,-2,2)

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Energy Properties

Formation Energy/atom

-0.75178

eV/atom

Energy/atom

-27.32356

eV/atom

Energy above Hull

0.0000

eV/atom

Uncorrected Energy

-27.3236

eV/atom

Volume/atom

16.63

Å³

c/a Ratio

1.2259

Electronic Properties

Metallic

Metal

Band Gap

Direct Gap

CBM

N/A

Magnetic Properties

Magnetic

Yes

Total Mag. Moment

2.0109

μB

Mag. Ordering

FiM

Mag. Sites

Magnetization/Volume

0.004320

μB/Å³

Elastic Properties

Elastic data not available

Feature Analysis

Composition Overview

Element Composition (atomic fraction)

Composition Info

Major / Matrix Element

Al · 0.643

Element Family

PostTransition-Noble

Solute Fraction

0.357

Interstitial Fraction

0.000

High-Entropy Alloy Features

Composite Radar (normalized)

Element-Class Share

Mix Entropy ΔS/R

1.0285

HEA criterion (>1.0 = high entropy)

Mix Entropy ΔS

8.5511

J/mol·K

Ω Parameter

1.8468

Ω > 1.1 favors solid solution

Atomic Size Mismatch δr

9.478%

δr < 6.6% favors single-phase solid solution

Electronegativity Diff Δχ

0.2531

smaller = more stable mixing

VEC

4.417

valence electron concentration, affects phase stability

Mix Enthalpy ΔH_mix

-6.901

kJ/mol; negative = exothermic mixing

Entropy Norm

0.7419

SS Former

Phase Tendency

Related Tasks

Related computation task IDs (1)

aaahfjal

Citation & References

Materials Project Page

https://materialsproject.org/materials/mp-3292807

Reference Citation

The crystal structure and related material properties of Pa2Al9Ir2Os were obtained from the Materials Project database (MP-ID: mp-3292807, 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_Pa2Al9Ir2Os
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.57186737
_cell_length_b   7.57183095
_cell_length_c   9.28234730
_cell_angle_alpha   90.00000000
_cell_angle_beta   90.00000000
_cell_angle_gamma   118.93535482
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Pa2Al9Ir2Os
_chemical_formula_sum   'Pa4 Al18 Ir4 Os2'
_cell_volume   465.74932121
_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
  Pa  Pa0  1  0.99675567  0.68706441  0.25000000  1.0
  Pa  Pa1  1  0.00324433  0.31293559  0.75000000  1.0
  Pa  Pa2  1  0.68706503  0.99676364  0.25000000  1.0
  Pa  Pa3  1  0.31293497  0.00323636  0.75000000  1.0
  Al  Al4  1  0.14052514  0.14054835  0.25000000  1.0
  Al  Al5  1  0.85947486  0.85945165  0.75000000  1.0
  Al  Al6  1  0.00492221  0.34084831  0.07713695  1.0
  Al  Al7  1  0.99507779  0.65915169  0.92286305  1.0
  Al  Al8  1  0.99507779  0.65915169  0.57713695  1.0
  Al  Al9  1  0.34082579  0.00491324  0.42283717  1.0
  Al  Al10  1  0.00492221  0.34084831  0.42286305  1.0
  Al  Al11  1  0.65917421  0.99508676  0.57716283  1.0
  Al  Al12  1  0.65917421  0.99508676  0.92283717  1.0
  Al  Al13  1  0.34082579  0.00491324  0.07716283  1.0
  Al  Al14  1  0.33516597  0.33517575  0.54365246  1.0
  Al  Al15  1  0.66483403  0.66482425  0.45634754  1.0
  Al  Al16  1  0.66483403  0.66482425  0.04365246  1.0
  Al  Al17  1  0.33516597  0.33517575  0.95634754  1.0
  Al  Al18  1  0.34610417  0.55457393  0.25000000  1.0
  Al  Al19  1  0.65389583  0.44542607  0.75000000  1.0
  Al  Al20  1  0.55458655  0.34611063  0.25000000  1.0
  Al  Al21  1  0.44541345  0.65388937  0.75000000  1.0
  Ir  Ir22  1  0.67325780  0.32667089  0.00000172  1.0
  Ir  Ir23  1  0.32674220  0.67332911  0.99999828  1.0
  Ir  Ir24  1  0.32674220  0.67332911  0.50000172  1.0
  Ir  Ir25  1  0.67325780  0.32667089  0.49999828  1.0
  Os  Os26  1  0.00000000  0.00000000  0.00000000  1.0
  Os  Os27  1  0.00000000  0.00000000  0.50000000  1.0

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