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{"@context":"https://schema.org","@type":"QAPage","mainEntity":{"@type":"Question","name":"Questions about the implementation of DQterm","text":"
Hi,
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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.
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the constans of CDQ  have significant differences with original paper.
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pub const CDQ: [[f64; 2]; 3] = [\n    [0.795009692, -2.099579397],\n    [3.386863396, -5.941376392],\n    [0.475106328, -0.178820384],\n];
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For the implementation of polar term in feos, there are differences with original paper for other constans too, like ADQ, BDQ, ...
\nbut the differences is small, and i think it might be introduced from rounding off.
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the sign of phi3 is different from original paoper.
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                for k in 0..p.ndipole {\n                    let dk = p.dipole_comp[k];\n                    phi3 += rho[di] * rho[qj] * rho[dk] * mu2_term[i] * q2_term[j] * mu2_term[k]\n                        / (p.sigma_ij[[di, qj]] * p.sigma_ij[[di, dk]] * p.sigma_ij[[qj, dk]])\n                            .powi(2)\n                        * triplet_integral_ijk_dq(mdqd[[i, j, k]], &etas, &CDQ);\n                }\n                for k in 0..p.nquadpole {\n                    let qk = p.quadpole_comp[k];\n                    phi3 += rho[di] * rho[qj] * rho[qk] * mu2_term[i] * q2_term[j] * q2_term[k]\n                        / (p.sigma_ij[[di, qj]] * p.sigma_ij[[di, qk]] * p.sigma_ij[[qj, qk]])\n                            .powi(2)\n                        * ALPHA\n                        * triplet_integral_ijk_dq(mdqq[[i, j, k]], &etas, &CDQ);\n                }
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The sign of original paper is negative, but the sign of feos positive, I don't know if it's a bug.
","upvoteCount":1,"answerCount":2,"acceptedAnswer":{"@type":"Answer","text":"
Hi,
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thanks for the questions. We will check the sign of $A_3^\\text{DQ}$ and come back to you with an answer.
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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.
","upvoteCount":1,"url":"https://github.com/feos-org/feos/discussions/294#discussioncomment-14116132"}}}