CosmoRSMixture¶

class CosmoRSMixture(mixture_components=None)¶

Create a mixture to be used as input in COSMO-RS methods. This object takes a list of tuples of input. Each tuple specifies first mixture component as either a CosmoRealSpecies or a MoleculeConfiguration. Secondly the mole fraction of the component is given, as a float ranging from 0 to 1. The mole fractions must add to 1.

Parameters:: mxiture_components (Sequence of tuples.) – The list of mixture components.

addMixtures(ratio, other)¶

Add two mixtures with a given ratio into a new mixture. Duplicates are added together into the one component.

Parameters:

ratio (float) – The fraction of the current mixture in the final one. The ratios of the two components should add to 1.
other ([type]) – The other component to be added to the new mixture.

Returns:

The new mixture created by adding the given two together. If both mixtures share a common component, these will be added together in the new mixture.

Return type:

CosmoRSMixture

componentMoleFraction(index)¶

Return a specific component mole fraction.

Parameters:: index (int) – The index of the mole fraction to return.
Returns:: The requested mole fraction.
Return type:: float

componentSpecies(index)¶

Return a specific component species.

Parameters:: index (int) – The index of the component to return.
Returns:: The requested species.
Return type:: CosmoRealSpecies

components()¶

Returns:: The components in the mixture, given as tuples of species and mole fraction.
Return type:: Sequence of tuples

density()¶

Returns:: The molar mass weighted density of the mixture.
Return type:: PhysicalQuantity of type mass per volume

molarMass()¶

The mole fraction weighted molar mass of the mixture.

Returns:: The mole fraction weighted molar mass of the mixture.
Return type:: PhysicalQuantity of type mass per mole.

molarVolume()¶

The mole fraction weighted molar volume of the mixture.

Returns:: The mole fraction weighted molar mass of the mixture.
Return type:: PhysicalQuantity of type mass per mole.

moleFractions()¶

Returns:: The mole fractions of each component.
Return type:: Sequence of float

numberOfComponents()¶

Returns:: The number of components in the mixture.
Return type:: int

species()¶

Returns:: The species included in the mixture.
Return type:: Sequence of CosmoRealSpecies

uniqueString()¶: Return a unique string representing the state of the object.

Usage Examples¶

Create a CosmoRSMixture object.

# Create a mixture.
mixture = CosmoRSMixture([
    (water, 0.6), (methanol, 0.4)
])

# Get the mixture density.
density = mixture.density()
nlprint(f'The density of the mixture is {density}')

# Get the molar volume.
molar_volume = mixture.molarVolume()
nlprint(f'The molar volume of the mixture is {molar_volume}')

# Get the molar mass.
molar_mass = mixture.molarMass()
nlprint(f'The molar mass of the mixture is {molar_mass}')

# Create another mixture.
another_mixture = CosmoRSMixture([
    (methanol, 0.4), (acetonitrile, 0.6)
])

# Combine them to create a new mixture.
new_mixture = mixture.addMixtures(0.5, another_mixture)
for i, x in enumerate(new_mixture.moleFractions()):
    nlprint(f'The mole fraction of component {i} is {x}')

mixture_example.py

Notes¶

The CosmoRSMixture object contains information about a mixture composition. The object can be passed on to any other solvent related COSMO-RS object such as LiquidEquilibrium. The molar mass of the mixture is defined as the weighted molar mass of the mixture, \(\overline{M}\).

\[\overline{M} = \sum_i x_i M_i\]

Here \(M\) is the molar mass and \(x\) the mole fraction of component species \(i\).

It is also possible to calculate the weighted molar volume of a solvent mixture \(\overline{V_m}\). \(V_m\) is defined as the volume occupied by 1 mole of species. This property can be determined based on the individual component densities their respective mole fractions.

\[\overline{V_m} = \sum_i x_i V_{m,i}\]

If all of the component species are provided with densities, the molar volume is calculated as

\[V_{m,i} = \frac{M_i}{\rho_i}\]

Here \(\rho\) is the density. If the density is not given for a species the molar volume is approximated from the COSMO cavity volume.

\[V_{m,i} = N_A V^{COSMO}_i\]

\(N_A\) is Avogadro constant.

The mixture density is then calculated based on the previous properties.

\[\rho = \frac{\overline{M}}{\overline{V_m}}\]

Finally, CosmoRSMixture objects may be combined to form a new mixture. This is done using addMixtures method where a mixture ratio is also needed. If the mixtures have a component species in common this will be added together to form a single component of the new mixture.