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fix: young's modulus unit #4436

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fix: young's modulus unit #4436

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47dde4f
fix: young's modulus unit
anyangml Jun 12, 2025
d103b48
Merge branch 'master' into master
shyuep Jun 16, 2025
23b4c82
Merge branch 'master' into master
shyuep Jun 16, 2025
1ca9f88
fix: update UT values
anyangml Jun 17, 2025
7eb7db6
Merge branch 'master' into master
anyangml Jul 3, 2025
b70a6e0
Merge branch 'master' into master
shyuep Nov 7, 2025
6a89179
fix: update doc
anyangml Nov 9, 2025
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4 changes: 3 additions & 1 deletion src/pymatgen/analysis/elasticity/elastic.py
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Original file line number Diff line number Diff line change
Expand Up @@ -135,6 +135,8 @@ class ElasticTensor(NthOrderElasticTensor):
in units of eV/A^3.
"""

eV_A3_to_GPa = Unit("eV ang^-3").get_conversion_factor(Unit("GPa"))

def __new__(cls, input_array, tol: float = 1e-4) -> Self:
"""
Create an ElasticTensor object. The constructor throws an error if the shape of
Expand Down Expand Up @@ -201,7 +203,7 @@ def y_mod(self) -> float:
Calculates Young's modulus (in SI units) using the
Voigt-Reuss-Hill averages of bulk and shear moduli.
"""
return 9.0e9 * self.k_vrh * self.g_vrh / (3 * self.k_vrh + self.g_vrh)
return 9.0e9 * self.k_vrh * self.g_vrh * self.eV_A3_to_GPa / (3 * self.k_vrh + self.g_vrh)
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@esoteric-ephemera esoteric-ephemera Nov 7, 2025 •
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@anyangml I would change the docstr to:

Calculates Young's modulus using Voigt-Reuss-Hill averages of bulk and shear moduli.

and remove the conversion to GPa here (and elsewhere where SI units are reported):

return 9* self.k_vrh * self.g_vrh / (3 * self.k_vrh + self.g_vrh)


def directional_poisson_ratio(self, n: ArrayLike, m: ArrayLike, tol: float = 1e-8) -> float:
"""
Expand Down
4 changes: 2 additions & 2 deletions tests/analysis/elasticity/test_elastic.py
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Expand Up @@ -94,7 +94,7 @@ def test_properties(self):
# voigt notation tensor
assert_allclose(self.elastic_tensor_1.voigt, self.voigt_1)
# young's modulus
assert self.elastic_tensor_1.y_mod == approx(54087787667.160583)
assert self.elastic_tensor_1.y_mod == approx(8665818958507.804)

# prop dict
prop_dict = self.elastic_tensor_1.property_dict
Expand Down Expand Up @@ -127,7 +127,7 @@ def test_structure_based_methods(self):
assert self.elastic_tensor_1.snyder_opt(struct) == approx(0.18937465)
assert self.elastic_tensor_1.snyder_total(struct) == approx(18.25064540)
# Clarke
assert self.elastic_tensor_1.clarke_thermalcond(struct) == approx(0.3450307)
assert self.elastic_tensor_1.clarke_thermalcond(struct) == approx(4.367299105244635)
# Cahill
cahill_thermal_cond = self.elastic_tensor_1.cahill_thermalcond(struct)
assert cahill_thermal_cond == approx(0.37896275)
Expand Down