COSMO-RS and COSMO-SAC parameters¶

COSMO-RS general parameters¶

CRSPARAMETERS
  {RAV         rav}
  {APRIME      aprime}
  {FCORR       fcorr}
  {CHB         chb}
  {SIGMAHBOND  sigmahbond}
  {AEFF        aeff}
  {LAMBDA      lambda}
  {OMEGA       omega}
  {ETA         eta}
  {CHORTF      chortf}
  {combi1998 | combi2005}
  {hb_all    | hb_hnof}
  {hb_temp   | hb_notemp}
  {fast      | nofast}
End

The ADF default values are optimized parameters for ADF calculations. The Klamt values can be found in Ref. [1]. See also Ref. [1] for the meaning of the parameters.

chortf

See Ref. [1] for the definitions: \(\sigma_v^\perp = \sigma_v^0 - c^\perp \sigma_v\)

combi1998 | combi2005

If the subkey combi1998 is included a thermodynamically inconsistent combinatorial contribution to the chemical potential \(\mu_i^{comb}\) of Ref. [1] is used. If the subkey combi2005 is included (default) a thermodynamically consistent combinatorial contribution of Ref. [3] is used. See the section on the combinatorial term and Ref. [3].

hb_all | hb_hnof

If the subkey hb_all is included hydrogen bond interaction can be included between segments that belong to H atoms and all other segments. If the subkey hb_hbnof is included (default) hydrogen bond interaction can be included only between segments that belong to H atoms that are bonded to N, O, or, F, and segments that belong to N, O, or F atoms.

hb_temp | hb_notemp

If the subkey hb_notemp is included the hydrogen bond interaction is not temperature dependent, as in Ref. [1]. If the subkey hb_temp is included (default) the hydrogen bond interaction is temperature dependent, as in Ref. [3]. See the section on the temperature dependent hydrogen bond interaction and Ref. [3].

fast | nofast

If the subkey fast is included the fast approximation is used. This fast approximation is the default. Use nofast for the original approach. See the section on the fast approximation for COSMO-RS calculations.

Links COSMO-RS GUI tutorial: set COSMO-RS parameters [1]

COSMO-RS element specific parameters¶

DISPERSION
  {H  dispH}
  {C  dispC}
  {N  dispN}
  {...}
End

The following table gives the element specific dispersion constants. The ADF default values are optimized parameters for ADF calculations. The Klamt values can again be found in Ref. [1]. The constants for F, Si, P, S, Br, and I in the ADF defaults were only fitted to a small number of experimental values or taken from Ref. [3].

Note that not for all elements in the periodic system COSMO-RS parameters were fitted.

Links COSMO-RS GUI tutorial: set COSMO-RS parameters [1]

COSMO-SAC general parameters¶

The ADF COSMO-RS program can calculate activity coefficients using the COSMO-SAC 2013-ADF model, based on Ref. [4]. Like in the COSMO-RS method, pure compound vapor pressures can be given as input, for example, if experimental values are available. If these values are not specified then the pure compound vapor pressure will be calculated according to the COSMO-SAC 2013-ADF model. This part of the COSMO-SAC 2013-ADF has been implemented in ADF2016. The COSMO-SAC 2013-ADF parameters in Ref. [4] are optimized parameters for use with ADF COSMO result files. The authors of Ref. [6] reoptimized the revised COSMO-SAC model [5] parameters for use with ADF COSMO result files, which is called here the COSMO-SAC 2016-ADF method. Note that the earlier COSMO-SAC papers [7] [5] do not include parameters that were optimized for use with ADF COSMO result files. The key COSMOSAC2013 needs to be included if one wants to do a COSMO-SAC 2013-ADF calculation. The key COSMOSACDHB needs to be included if one wants to do a COSMO-SAC DHB-ADF calculation. For other COSMO-SAC methods one needs to include the key COSMOSAC.

COSMOSAC2013 | COSMOSAC | COSMOSACDHB
SACPARAMETERS
  {AEFF        aeff}
  {FDECAY      fdecay}
  {SIGMA0      sigma0}
  {RN          rn}
  {QN          qn}
  {AES         aes}
  {BES         bes}
  {COHOH       cohoh}
  {COTOT       cotot}
  {COHOT       cohot}
  {RAV         rav}
  {QS          qs}
  {rhbcut      rhbcut}
  {hb_temp   | hb_notemp}
End

See also Refs. [4] [5] for the meaning of the parameters a_eff , f_decay , \(\sigma\)₀ , r, q, A_ES , B_ES , c_OH-OH , c_OT-OT , c_OH-OT , r_av , q_s . The parameter names in [7] have been translated into parameter names used in Ref. [5], by calculating A_ES from 0.3 f_pol a_eff ^3/2 /(2\(\epsilon_0\) ), using B_ES = 0, and using c_OH-OH = c_OT-OT = c_OH-OT = c_hb . The parameters f_decay and r are not used in COSMO-SAC 2013-ADF [4]. The parameters r_av and q_s are only used in COSMO-SAC 2013-ADF. The element specific COSMO-SAC 2013-ADF epsilon constants can be set with the block key EPSILON. These element specific epsilon constants can not be used in ADF’s implementation of earlier COSMO-SAC methods. The parameter rhbcut is only used in COSMO-SAC DHB-ADF [8]. Note that the parameters for COSMO-SAC DHB-ADF were reoptimized by Chen et al., and are different than in Ref. [8].

hb_temp | hb_notemp

If the subkey hb_notemp is included (default) the hydrogen bond interaction is not temperature dependent, as in Refs. [7] [5] [4]. If the subkey hb_temp is included the temperature dependence of the hydrogen bond interaction f_hb (T) is the same as is described in the section on the temperature dependent hydrogen bond interaction.

Except for COSMO-SAC 2013-ADF, some COSMO-RS specific parameters are used in the next COSMO-SAC methods:

COSMOSAC
SACPARAMETERS
  ...
  {OMEGA       omega}
  {ETA         eta}
End

In ADF2016 these parameters are not used in the COSMO-SAC 2013-ADF method, only in the ADF implementation of the other COSMO-SAC methods. The parameters \(\omega\), \(\eta\) and the element specific COSMO-RS dispersion constants are taken from the COSMO-RS model. The element specific COSMO-RS dispersion constants can be set with the block key DISPERSION. \(\omega\), \(\eta\), and the element specific COSMO-RS dispersion constants are used in a COSMO-RS like method for the calculation of pure compound vapor pressures.

COSMO-SAC element specific parameters¶

COSMOSAC2013
EPSILON
  {H  epsH}
  {C  epsC}
  {N  epsN}
  {...}
End

The following table gives the element specific epsilon constants in case of COSMO-SAC 2013-ADF, see Ref. [4]. Like in the COSMO-RS method, pure compound vapor pressures can be given as input, for example, if experimental values are available. In these values ar not given, in ADF2016 the pure compound vapor pressure will be approximated using the the COSMO-SAC 2013-ADF method, which depend on these element specific epsilon constants. These constants will also have an effect on the calculated activity coefficients in case of a mixture. Note that these only have an effect in the ADF’s COSMO-SAC 2013-ADF implementation.

Note that not for all elements in the periodic system COSMO-SAC 2013-ADF parameters were fitted.

If one leaves the EPSILON block keyword empty the contribution of the mixture dispersion to the activity coefficient will be zero.

EPSILON
End

Links COSMO-RS GUI tutorial: Expert option: set COSMO-SAC 2013-ADF parameters [1]

Technical and accuracy parameters¶

TECHNICAL
  {RSCONV rsconv}
  {SACCONV sacconv}
  {MAXITER maxiter}
  {BPCONV bpconv}
  {BPMAXITER bpmaxiter}
  {SOLCONV solconv}
  {SOLMAXITER solmaxiter}
  {SOLXILARGE solxilarge}
  {EHDELTAT ehdeltaT}
End

rsconv

Convergence criterion in kcal/mol in chemical potential calculation, not used in COSMO-SAC 2013-ADF. Default value 1e-7 kcal/mol.

sacconv

Convergence criterion in activity coefficient calculation, only used in COSMO-SAC 2013-ADF. Default value 1e-7.

maxiter

Maximum number of cycles in chemical potential or activity coefficients calculation. Default value 10000.

bpconv

Convergence criterion (bar) for isobar or solvent boiling point calculation. Default value 1e-6 bar.

bpmaxiter

Maximum number of cycles in isobar or solvent boiling point calculation. Default value 40.

solconv

Convergence criterion (molar fraction) used in solubility calculations. Default value 1e-5 molar fraction.

solmaxiter

Maximum number of cycles in solubility calculation. Default value 40.

solxilarge

Threshold for (im-)miscibility (molar fraction) in solubility calculations. Above this value the mixture is considered to be fully miscible. Default value 0.99.

ehdeltaT

\(\Delta T\) (Kelvin) used in the calculation of the excess enthalpy using the Gibbs-Helmholtz equation and in the calculation of the enthalpy of vaporization using the Clausius-Clapeyron equation using a numerical derivative with respect to T. Default value 1.0 Kelvin.

Links COSMO-RS GUI tutorial: set COSMO-RS or COSMO-SAC 2013-ADF parameters [1]

References