# Properties¶

## Vapor pressure¶

The vapor pressure of a mixture can be calculated with:

PROPERTY vaporpressure
End


In case of a mixture the mole fraction of each compound of the solvent should be given with the subkey FRAC1 of the key COMPOUND for each compound. In case of a mixture also activity coefficients, and excess energies are calculated.

To calculate pure compound vapor pressures for more than one compound use:

PROPERTY purevaporpressure
End


It is possible to calculate the vapor pressure for a temperature range, see key TEMPERATURE.

The input pure compound vapor pressure will be used in the calculation of the vapor pressure of this compound if it is supplied with the key COMPOUND for this compound. If it is not specified then it will be approximated using the COSMO-RS method.

Links COSMO-RS GUI tutorial: solvent vapor pressure [1, 2]

## Boiling point¶

The boiling point of a mixture can be calculated with the block key:

PROPERTY boilingpoint
End


In case of a mixture the mole fraction of each compound of the solvent should be given with the subkey FRAC1 of the key COMPOUND for each compound. In case of a mixture also activity coefficients, and excess energies are calculated.

To calculate pure compound boiling points for more than one compound use:

PROPERTY pureboilingpoint
End


It is possible to calculate the boiling temperature for a pressure range, see key PRESSURE.

The input pure compound vapor pressure will be used in the calculation of the vapor pressure of this compound in the mixture if it is supplied with the key COMPOUND for this compound. If it is not specified then it will be approximated using the COSMO-RS method.

The COSMO-RS calculation of the boiling temperature of a solvent is performed with an iterative method. The temperature is varied until the calculated vapor pressure is within a certain threshold of the desired pressure.

Links COSMO-RS GUI tutorial: boiling point of a solvent [1]

## Solvent flash point¶

The flash point (lower flammable limit) of a compound is the lowest temperature at which the vapor of the compound forms an ignitable mixture in air. The COSMO-RS module can calculate the flash point of a mixture. The COSMO-RS module, however, does not calculate or predict the flash point of pure compounds. The COSMO-RS method is used to calculate the partial vapor pressures of each compound in the mixture, and it uses Le Chatelier’s mixing rule to calculate the flash point of this mixture in the gas phase. Input pure compound flash points should be provided by the user, with the subkey FLASHPOINT flashpoint of the key COMPOUND.

PROPERTY flashpoint
End


The mole fraction of each compound of the solvent should be given with the subkey FRAC1 of the key COMPOUND for each compound.

## Partition coefficients (LogP)¶

The partition coefficient of a compound in a mixture of two immiscible solvents, can be calculated with:

PROPERTY logp
{VOLUMEQUOTIENT volumequotient}
End

volumequotient
If the subkey VOLUMEQUOTIENT is included the volumequotient will be used for quotient of the molar volumes of solvent 1 and solvent 2 instead of calculated values.

The mole fraction of each compound of the solvent 1 and solvent 2 should be given with the subkey FRAC1 and subkey FRAC2 of the key COMPOUND for each compound, respectively. In case of partly miscible liquids, like, for example, the Octanol-rich phase of Octanol and Water, both components have nonzero mole fractions. The compounds that are included without a given mole fraction are considered to be infinite diluted solutes. The partition coefficients are calculated for all compounds.

One can use some compounds that are present in $ADFHOME/atomicdata/ADFCRS (Water, 1-Octanol, Benzene, Ethoxyethane, Hexane), or one can use compounds from the ADFCRS-2010 database. For example, for Octanol/Water partition coefficients one can use: Property logp VolumeQuotient 4.93 End Compound "$ADFHOME/atomicdata/ADFCRS/1-Octanol.coskf"
frac1 0.725
End
frac1 0.275
frac2 1.0
End


Links COSMO-RS GUI tutorial: partition coefficients (log P) [1, 2], Octanol-Water partition coefficients (log POW ) [1]

## Activity coefficients solvent and solute¶

The mole fraction of each compound of the solvent should be given with the subkey FRAC1 of the key COMPOUND for each compound. The compounds that are included without a given mole fraction are considered to be infinite diluted solutes. The activity coefficients are calculated for all compounds.

PROPERTY activitycoef
{DENSITYSOLVENT densitysolvent}
End

densitysolvent
If the subkey DENSITYSOLVENT is included the densitysolvent will be used for the density of the solvent (kg/L) instead of calculated values. Relevant for the calculation of the Henry’s law constant.

The input pure compound vapor pressure will be used in the calculation of the partial vapor pressure of this compound in the mixture if it is supplied with the key COMPOUND for this compound. If it is not specified then it will be approximated using the COSMO-RS method. Relevant for the calculation of the Henry’s law constant.

The Henry’s law constants are calculated in 2 units. The Henry’s law constant kH is the ratio between the liquid phase concentration of a compound and its partial vapor pressure in the gas phase. The dimensionless Henry’s law constant kH cc is the ratio between the liquid phase concentration of a compound and its gas phase concentration.

Also calculated is $$\Delta G_{solv}^{liq-solv}$$ , which is the solvation Gibbs free energy from the pure compound liquid phase to the solvated phase, and $$\Delta G_{solv}^{gas-solv}$$ , which is the solvation Gibbs free energy from the pure compound gas phase to the solvated phase, with a reference state of 1 mol/L in both phases. In addition a Gibbs free energy is calculated which is the free energy of the solvated compound with respect to the gas phase energy of the spin restricted spherical averaged neutral atoms, the compound consist of. Note that zero-point vibrational energies are not taken into account in the calculation of this free energy. This energy could be used in the calculation of $$pK_a$$ values.

Links COSMO-RS GUI tutorial: activity coefficients [1, 2], solvation free energies [1], Henry’s law constants [1], $$pK_a$$ values [1]

## Solubility¶

The solubility of solutes in 1 mixture can be calculated with:

PROPERTY solubility
End


The mole fraction of each compound of the solvent should be given with the subkey FRAC1 of the key COMPOUND for each compound, and should add up to 1.0. The solutes should have zero molar fraction in the solvent. The solubility of 1 solute in pure solvents can be calculated with

PROPERTY puresolubility
End


The mole fraction of each pure solvent should be 1.0, and should be set the subkey FRAC1 of the key COMPOUND for each compound. The solute should have zero molar fraction in the solvent. It is possible to calculate the solubility of a solute at a temperature range, see key TEMPERATURE.

For solubility calculations of a solid compound one should add the pure compound melting point $$T_m$$ , pure compound enthalpy of fusion $$\Delta H_{fus}$$ , and optionally the pure compound heat capacity of fusion $$\Delta C_p$$ using the subkeys meltingpoint, hfusion, and cpfusion, respectively, of the key COMPOUND for this compound. The COSMO-RS method does not predict these $$\Delta H_{fus}$$, $$\Delta C_p$$, or $$T_m$$ .

The assumption made in the solubility calculation may be invalid in case of a solubility of a liquid in a solvent, especially if the solubility of the solvent in the liquid is high. For binary systems one may check this by calculating the miscibility gap in the binary mixture of the two liquids. It is possible to calculate the solubility of a gas in a solvent, if one adds the subkey isobar and adds the partial vapor pressure partialvaporpressure (bar) of the gas as argument for the key PRESSURE:

PROPERTY solubility
isobar
End

PRESSURE partialvaporpressure


The solubility of a gas in a solvent can also be calculated using Henry’s law, which is valid for ideal dilute solutions, see see the key PROPERTY activitycoef. The COSMO-RS calculation of the solubility of a compound is performed with an iterative method, since the activity coefficient of the compound depends on the molar fraction of this compound.

Links COSMO-RS GUI tutorial: solubility [1, 2]

## Binary mixture (VLE/LLE)¶

The COSMO-RS module can automatically calculate properties of a binary mixture, by calculating these properties for a number of different compositions.

Exactly two compounds should be given in the input file.

PROPERTY binmixcoef
{Nfrac nfrac}
{isotherm | isobar | flashpoint}
End

nfrac
Number of different mixtures for which the binary mixture is calculated will be nfrac+5. Default value for nfrac is 10, which means 15 different mixtures.
isotherm | isobar |flashpoint
If the subkey isotherm is included (default) the binary mixture will be calculated at a fixed temperature. If the subkey isobar is included the binary mixture will be calculated at a fixed vapor pressure. If the subkey flashpoint is included the flash point of the binary mixture will be calculated.

The input pure compound vapor pressure will be used in the calculation of the partial vapor pressure of this compound in the mixture if it is supplied with the key COMPOUND for this compound. If it is not specified then it will be approximated using the COSMO-RS method.

In case of a miscibility gap (LLE) data of the 2 immiscible liquid phases will be calculated. Also information about possible azeotropes will be calculated. With the COSMO-RS GUI, activity coefficients, (partial) vapor pressures, and excess energies can be viewed.

Links COSMO-RS GUI tutorial: vapor-liquid diagram binary mixture (VLE/LLE) [1, 2]

## Ternary mixture (VLE/LLE)¶

The COSMO-RS module can automatically calculate properties of a ternary mixture, by calculating these properties for a number of different compositions. Exactly three compounds should be given in the input file.

PROPERTY ternarymix
{Nfrac nfrac}
{isotherm | isobar |flashpoint}
End

nfrac
Number of different mixtures for which the ternary mixture is calculated will be (nfrac+1)*(nfrac+2)/2. Default value for nfrac is 10, which means 55 different mixtures.
isotherm | isobar | flashpoint
If the subkey isotherm is included (default) the ternary mixture will be calculated at a fixed temperature. If the subkey isobar is included the ternary mixture will be calculated at a fixed vapor pressure. If the subkey flashpoint is included the flash point of the ternary mixture will be calculated.

The input pure compound vapor pressure will be used in the calculation of the partial vapor pressure of this compound in the mixture if it is supplied with the key COMPOUND for this compound. If it is not specified then it will be approximated using the COSMO-RS method.

In case of a miscibility gap liquid-liquid equilibrium (LLE) data such as tie lines and an approximate phase diagram, are calculated. With the COSMO-RS GUI, activity coefficients, (partial) vapor pressures, and excess energies can be viewed as a colormap in a 2-dimensional plot with 2 of the liquid compositions on the axes.

Links COSMO-RS GUI tutorial: ternary mixtures (VLE/LLE) [1]

## Solvents s1 - s2 Composition Line¶

The COSMO-RS module can linear interpolate between the compositions of solvent 1 and solvent 2, which both could be mixtures, and calculate properties, like activity coefficients, and excess energies. This property calculation does not calculate a possible miscibility gap. The mole fraction of each compound of the solvent 1 and solvent 2 should be given with the subkey FRAC1 and subkey FRAC2 of the key COMPOUND for each compound, respectively.

PROPERTY compositionline
{Nfrac nfrac}
{isotherm | isobar | flashpoint}
End

nfrac
Number of different mixtures of the 2 solvents is calculated will be (nfrac+1). Default value for nfrac is 10, which means 11 different mixtures.
isotherm | isobar | flashpoint
If the subkey isotherm is included (default) a fixed temperature will be used. If the subkey isobar is included a fixed vapor pressure will be used. If the subkey flashpoint is included the flashpoint will be calculated.

Links COSMO-RS GUI tutorial: A composition line between solvents s1 and s2 [1]