Questions about the implementation of DQterm #294
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Hi, I'm working for the implementation of polar term in our project, and have some questions about the implementaion of DQ polar term in feos.
pub const CDQ: [[f64; 2]; 3] = [
[0.795009692, -2.099579397],
[3.386863396, -5.941376392],
[0.475106328, -0.178820384],
];
For the implementation of polar term in feos, there are differences with original paper for other constans too, like ADQ, BDQ, ...
for k in 0..p.ndipole {
let dk = p.dipole_comp[k];
phi3 += rho[di] * rho[qj] * rho[dk] * mu2_term[i] * q2_term[j] * mu2_term[k]
/ (p.sigma_ij[[di, qj]] * p.sigma_ij[[di, dk]] * p.sigma_ij[[qj, dk]])
.powi(2)
* triplet_integral_ijk_dq(mdqd[[i, j, k]], &etas, &CDQ);
}
for k in 0..p.nquadpole {
let qk = p.quadpole_comp[k];
phi3 += rho[di] * rho[qj] * rho[qk] * mu2_term[i] * q2_term[j] * q2_term[k]
/ (p.sigma_ij[[di, qj]] * p.sigma_ij[[di, qk]] * p.sigma_ij[[qj, qk]])
.powi(2)
* ALPHA
* triplet_integral_ijk_dq(mdqq[[i, j, k]], &etas, &CDQ);
}
The sign of original paper is negative, but the sign of feos positive, I don't know if it's a bug. |
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Replies: 2 comments 1 reply
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Hi, thanks for the questions. We will check the sign of Regarding the constants - the constants in the code are consistent with those of the publication. They are simply divided by |
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Hi, Thanks for your answer about the constants, it's really helpful for our project. About the sign of The experimental data of bubble point was chosen from DOI:https://doi.org/10.1016/j.supflu.2015.02.003 
The parameters of carbon dioxide and acetone: CO2_QQ = PureRecord(
Identifier(name="carbon_dioxide"),
molarweight=0.0,
m=1.5131,
sigma=3.1869,
epsilon_k=163.33,
q=4.4,
)
ACETONE_DD = PureRecord(
Identifier(name="acetone"),
molarweight=0.0,
m=2.7447,
sigma=3.2742,
epsilon_k=232.99,
mu=2.88,
)when the sign was negative, the output looks weired: 
while when the sign is positive, the output looks better. 
so, out team decide to use positive sign in our project. and thanks for your help again. |
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Thank you for sharing your analysis, that is very helpful for us as well! |
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Hi,
thanks for the questions. We will check the sign of$A_3^\text{DQ}$ and come back to you with an answer.
Regarding the constants - the constants in the code are consistent with those of the publication. They are simply divided by$\pi^2$ . $A_3^\text{DQ}$ is then multiplied by $\pi^2$ before returning.