 # ccCA reference energy calculation correction

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 9:25:31 PM PDT - Mon, Sep 11th 2017 The CBS extrapolation uses single precision constants which should be coerced to double precision ones, as per suggestion from Edoapra. Without this change, the error is in 10s of microHartrees for small molecules and grows larger with increasing heavy atom count. A patch file for the 27746 release (from Fedora 24) appears below. ```--- src/ccca/ccca_utils.F.orig 2017-09-11 18:44:59.917105436 -0500 +++ src/ccca/ccca_utils.F 2017-09-11 18:49:41.625143653 -0500 @@ -674,17 +674,17 @@ E_Q = E_Q - HF_Q c c fit function: E(n) = E(inf) + B*exp(-1.63*n) - ErefHF=-0.243672155849*HF_T+1.243672155849*HF_Q + ErefHF=-0.243672155849d0*HF_T+1.243672155849d0*HF_Q c c fit function: E(lmax) = E(inf) + B/(lmax)^3 - ErefS3=ErefHF-0.729729729730*E_T+1.729729729730*E_Q + ErefS3=ErefHF-0.729729729730d0*E_T+1.729729729730d0*E_Q c c fit function: E(lmax) = E(inf) + B/(lmax+1/2)^4 - ErefS4=ErefHF-0.577163461538*E_T+1.577163461540*E_Q + ErefS4=ErefHF-0.577163461538d0*E_T+1.577163461540d0*E_Q c c fit function: E(n) = E(inf) + B*exp(-(n-1)) + C*exp(-(n-1)**2) - ErefP=ErefHF+0.034867106002*E_D-0.711622433526*E_T - \$ +1.676755327520*E_Q + ErefP=ErefHF+0.034867106002d0*E_D-0.711622433526d0*E_T + \$ +1.676755327520d0*E_Q ErefPS3=(ErefP+ErefS3)*0.5 DKcorr=DK-mp2vtz CVcorr=CV-E_T-HF_T ``` 