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Correct missing factor of pi in Z and alpha #722

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Merged
avcopan merged 1 commit into from
Mar 4, 2026
Merged

Correct missing factor of pi in Z and alpha #722

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6 changes: 4 additions & 2 deletions src/automol/etrans/_fxn.py
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Expand Up @@ -11,9 +11,11 @@ def troe_lj_collision_frequency(eps, sig, red_mass, temp):
""" Collision Frequency formula from Troe that uses
Lennard-Jones epsilons and sigma parameters

Z = sqrt( (8*kB*T)/(pi*mu) ) * sig^2 * omega
Z = pi * sqrt( (8*kB*T)/(pi*mu) ) * sig^2 * omega
omega = [ 0.7 + 0.5 log10( (kB*T)/eps ) ]^-1

See Eq. 12 from Jasper, J. Phys. Chem. A 2009, 113, 19, 5612-5619

:param eps: Target+Bath Lennard-Jones epsilon value (in hart)
:type eps: float
:param sig: Target+Bath Lennard-Jones sigma value (in bohr)
Expand All @@ -35,7 +37,7 @@ def troe_lj_collision_frequency(eps, sig, red_mass, temp):
kbt = phycon.KB * temp

# Prefactor term with physical constants and masses
pref1 = numpy.sqrt((8.0 * kbt) / (numpy.pi * red_mass))
pref1 = numpy.pi * numpy.sqrt((8.0 * kbt) / (numpy.pi * red_mass))

# Omega integral
omega_s = (0.7 + 0.52 * (numpy.log10(kbt / eps)))**(-1)
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2 changes: 1 addition & 1 deletion src/automol/tests/test_etrans.py
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Expand Up @@ -167,7 +167,7 @@ def test__estimate():
# Build the alpha parameters
edown_alpha, edown_n = automol.etrans.estimate.alpha(
n_eff, eps, sig, tgt_mass, bath_mass, collider_set)
ref_edown_alpha = 457.24552400133837
ref_edown_alpha = 457.24552400133837 / numpy.pi
ref_edown_n = 0.70088400006973
assert numpy.isclose(edown_alpha, ref_edown_alpha)
assert numpy.isclose(edown_n, ref_edown_n)
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