Mod:Hunt Research Group: Using SMD on ILs

This page explains how to use the SMD model to simulate an ionic liquid environment in Gaussian calculations. The SMD model is explained in detail in the original paper here.^[1] Its use on ILs is similarly explained here.^[2] Many useful solvent parameters are also available in this paper.

How to simulate a defined solvent environment

Gaussian has many previously defined solvent environments. A list is available at the bottom of this page.^[3] For example to use the pre-defined water environment simply insert the following keyword into the method line of your input file. The rest of your method line should specify your functional, basis set, optimisation/other type of calculation as usual.

scrf=(smd,solvent=water)

To use a different solvent to water change the solvent=water part to solvent=something else in the list.

How to simulate a generic solvent environment

The SMD model has many parameters. These are already defined inside Gaussian for the list of defined solvents. If you want to use a solvent not on the list e.g. an ionic liquid, you must define these parameters manually. In this case put the following into the method line:

scrf=(smd,solvent=generic)

Solvent parameters

Parameter	Symbol	Name in Gaussian input file
Dielectric constant	ε	eps
Index of refraction, squared	n²	epsinf
Macroscopic surface tension /cal mol^-1 Å^-2	γ	SurfaceTensionAtInterface
Abraham hydrogen bond acidity parameter	Σα₂^H	HBondAcidity
Abraham hydrogen bond basicity parameter	Σβ₂^H	HBondBasicity
Fraction of non-hydrogen atoms which are aromatic carbon atoms	φ	CarbonAromaticity
Fraction of non-hydrogen atoms which are electronegative halogen atoms	ψ	ElectronegativeHalogenicity

Notes on parameters

Surface tension

surface tension is the only parameter with units, those used in SMD are non-standard cal mol^-1Å^-2
the SI units are Jm^-2 or Nm^-1
typical units are dyn cm^-1 where 1 dyn = 1 g cm s^-2
as we tend to work in kJ/mol the energy part of this becomes not J but J/mol
1 dyn cm^-1 = 0.001N m^-1 = 0.001J m^-2
1 m = 1*10¹⁰Å and 1J=0.239cal and 1 mol^-1=6.022*10²³
1 dyn cm^-1 = 0.001*0.239cal*6.022*10²³mol^-1/(1*10^2*10Å²
and if you think about this 10²³ on top line cancels with 10²⁰ on bottom line leaving 10³ which cancels with the 0.001=10^-3 leaving us with 0.239*6.022=1.439
1 dyn cm^-1 = 1.439 cal mol^-1 Å^-2

Molar Volume

MolarVolume=x.x in cm³/mol
molecular volume in Å³ per molecule converted to cm³/mol
1cm = 1*10⁸Å, 1Å = 1*10^-8 cm
x Å³ per molecule = x*6.022*10²³mol^-1 *10^3*-8cm³ = x*6.022*10^-1cm³mol^-1

Kamlet-Taft vs Abraham H-bonding parameters

the SMD model requires Abraham H-bondonding parameters (Σα₂^H, Σβ₂^H)
however Kamlet-Taft (α, β) measurements are more commonly reported for ILs
a relationship between the parameters was investigated, giving the following equations:^[2]

Σα₂^H = 0.4098α + 0.0064

Σβ₂^H = 0.6138β + 0.0890

Previously the group has developed a simple method for calculating Kamlet-Taft parameters, and the instructions are here.^[4]

Types of SMD model for ILs

3 types of SMD for ILs have been defined.^[2]

SMD The standard SMD model. All parameters are determined for the particular IL (or a very similar one) being used as the solvent environment.
SMD-GIL The generic ionic liquid model. The average values above are used for all parameters, except φ and ψ, which are simply calculated from the chemical formula of the IL.
SMD-PGPThe partial generic parameters model. Any parameter which has been measured for that IL is used. For any parameters which you do not have values for, use the average values.

Example: [C₄C₁Im][NTf₂]

All parameters for this IL have been measured, and can be found in reference 2.^[2] That means we can use the standard SMD method.
To get a value for φ take the number of aromatic carbon atoms (3) and divide by the number of non-hydrogen atoms (25). φ = 0.12.
To get a value for ψ take the number of electronegative halogen atoms (6) and divide by the number of non-hydrogen atoms (25). ψ = 0.24.
To define these parameters place the following line at the bottom of the input file (include one blank line before and at least one blank line after):
eps=11.52 epsinf=2.037 SurfaceTensionAtInterface=53.97 HBondAcidity=0.259 HBondBasicity=0.238 CarbonAromaticity=0.12 ElectronegativeHalogenicity=0.24
see following data for other ILs

SMD input database

Here we will keep a database of SMD parameters used by the group. Please add any IL you use, so no-one else has to re-do the research for the parameters! Please follow the template provided so that it is clear where you get each value from.

SMD-GIL

all values from ^[2]

Name in Gaussian input file	Value	Reference	Comments/calculations
eps	11.50
epsinf (n²)	2.0449
SurfaceTensionAtInterface	61.24
HBondAcidity (α)	0.229
HBondBasicity (β)	0.265
CarbonAromaticity (φ)	compute for your system
ElectronegativeHalogenicity (ψ)	compute for your system
`eps=11.70 epsinf=2.0207 SurfaceTensionAtInterface=67.07 HBondAcidity=0.263 HBondBasicity=0.320 CarbonAromaticity=0.2000 ElectronegativeHalogenicity=0.2667`

[C₄C₁Im][BF₄]

all values from ^[2]

Name in Gaussian input file	Value	Comments/calculations
eps	11.70
epsinf n²)	2.0207	Value given in reference is n=1.4215, it has been squared to give epsinf=2.0207
SurfaceTensionAtInterface	67.07
HBondAcidity (α)	0.263	Kamlet-Taft 0.627
HBondBasicity (β)	0.320	Kamlet-Taft 0.376
CarbonAromaticity (φ)	0.2000	There are 15 non-H atoms, 3 are aromatic C atoms, value=3/15=0.2000
ElectronegativeHalogenicity (ψ)	0.2667	There are 15 non-H atoms, 4 are electronegative halogen atoms, value =4/15=0.2667
`eps=11.70 epsinf=2.0207 SurfaceTensionAtInterface=67.07 HBondAcidity=0.263 HBondBasicity=0.320 CarbonAromaticity=0.2000 ElectronegativeHalogenicity=0.2667`

[C₄C₁Im][PF₆]

all values from ^[2]

Name in Gaussian input file	Value	Comments/calculations
eps	11.40
epsinf n²)	1.9853	Value given in reference is n=1.4090, it has been squared to give epsinf=1.9853
SurfaceTensionAtInterface	70.24
HBondAcidity (α)	0.266	Kamlet-Taft 0.634
HBondBasicity (β)	0.216	Kamlet-Taft 0.207
CarbonAromaticity (φ)	0.1765	There are 17 non-H atoms, 3 are aromatic C atoms, value=3/17=0.1765
ElectronegativeHalogenicity (ψ)	0.3529	There are 17 non-H atoms, 4 are electronegative halogen atoms, value =6/17=0.3529
`eps=11.40 epsinf=1.9853 SurfaceTensionAtInterface=70.24 HBondAcidity=0.266 HBondBasicity=0.216 CarbonAromaticity=0.1765 ElectronegativeHalogenicity=0.3529`

[C₄C₁Im][NTf₂]

all values from ^[2]

Name in Gaussian input file	Value	Reference	Comments/calculations
eps	11.52	^[5]
epsinf n²)	2.0366	^[6]	Value given in reference is n=1.4271, it has been squared to give epsinf=2.0366
SurfaceTensionAtInterface	53.97	^[6]
HBondAcidity (α)	0.259	^[1]	Kamlet-Taft 0.617
HBondBasicity (β)	0.238	^[1]	Kamlet-Taft 0.243
CarbonAromaticity	0.1200		There are 25 non-H atoms, 3 are aromatic C atoms, value =3/25=0.1200
ElectronegativeHalogenicity	0.2400		There are 25 non-H atoms, 6 are electronegative halogen atoms, value =6/25=0.2400
`eps=11.52 epsinf=2.0366 SurfaceTensionAtInterface=53.97 HBondAcidity=0.259 HBondBasicity=0.238 CarbonAromaticity=0.1200 ElectronegativeHalogenicity=0.2400`

[C₄C₁Im][OTf]

Name in Gaussian input file	Value	Reference	Comments/calculations
eps	12.90	^[7]	Page 1495, number 11 on the list.
epsinf n²)	2.0665	^[8]	n=1.43755, has been squared to give epsinf=2.0665. Can be found in Table 1, 3rd row.
SurfaceTensionAtInterface	unknown
HBondAcidity (α)	0.263	^[2] ^[1]	Kamlet-Taft 0.625
HBondBasicity (β)	0.374	^[2] ^[1]	Kamlet-Taft 0.464
CarbonAromaticity	0.1667	-	There are 18 non-H atoms, 3 are aromatic C atoms, value=3/18=0.1667.
ElectronegativeHalogenicity	0.1667	-	There are 18 non-H atoms, 3 are electronegative halogen atoms, value=3/18=0.1667.
`eps=12.90 epsinf=2.0665 SurfaceTensionAtInterface=XX HBondAcidity=0.263 HBondBasicity=0.374 CarbonAromaticity=0.1667 ElectronegativeHalogenicity=0.1667`

[C₄C₁Im][SCN]

Name in Gaussian input file	Value	Reference	Comments/calculations
eps	13.70	^[7]
epsinf (n²)	2.3691	^[9]	n=1.53921, has been squared to give epsinf=2.3691 (error in some database calcs with n=1.5436 n2=2.3827)
SurfaceTensionAtInterface	68.34	^[9]	η=45.41 (mN.m^-1) converts to 45.41*1.439= cal mol-1 Å-2=65.34
HBondAcidity (α)	0.18		Kamlet-Taft 0.43
HBondBasicity (β)	0.52		Kamlet-Taft 0.71
CarbonAromaticity	0.2308		There are 13 non-H atoms, 3 are aromatic C atoms, value=3/13=0.2308
ElectronegativeHalogenicity	0.0		There are no electronegative halogen atoms, value=0.0
`eps=13.70 epsinf=2.3691 SurfaceTensionAtInterface=68.34 HBondAcidity=0.18 HBondBasicity=0.52 CarbonAromaticity=0.2308 ElectronegativeHalogenicity=0.0`

Molten salt [Li⁺,Na⁺,K⁺][CO₃^2-]

Name in Gaussian input file	Value	Reference	Comments/calculations
MolarVolume	57	^[10]	molar volume Li₂CO₃ 68 Na₂CO₃ 92 K₂CO₃ 124 Å³/molecule, average is 95 and 95*0.6022=57 at T=1.1Tm
Tabs	900		Absolute Temperature in K ie 298+600≈900
???			ThermalExansionCoefficient estimate 20*10^-6 K^-1at T=1.1Tm (this is not working!)
eps	3	^[10]	estimated value
epsinf n²)	2.25		refractive index Na₂CO₃ 1.489-1.535,^[11] Li₂CO₃ 1.428-1.572^[12] K₂CO₃ 1.426-1.541^[13] taking a "mid" value 1.5²=2.25
SurfaceTensionAtInterface	273	^[10]	used surface tension of Na/K/CO₃ mixture 50 mol % K₂CO₃ at 810 ºC , 190.0 dynes/cm
HBondAcidity (α)	0.00	-	There are no H-atoms so H-bond acidity is zero H-bond basicity computations result in proton transfer, NO₃ ≈0.74-0.81, Cl ≈0.95-0.98, we assume it is even stronger due to -2 charge
HBondBasicity (β)	0.99
CarbonAromaticity	0.00	-	There are no aromatic C atoms
ElectronegativeHalogenicity	0.00	-	There are no halogen atoms
Stoichiometry=C2O62Li2Na2K2 MolarVolume=57.0 Tabs=900 eps=3.0 epsinf=2.25 SurfaceTensionAtInterface=273 HBondAcidity=0.0 HBondBasicity=0.99 CarbonAromaticity=0.0 ElectronegativeHalogenicity=0.0

Bismuth halometallate ionic liquid, parameterised for [C₂C₁Im][BiCl₄]

Name in Gaussian input file	Value	Reference	Comments/calculations
eps	11.5	^[2]	From SMD-GIL
epsinf	2.04	^[2]	From SMD-GIL
SurfaceTensionAtInterface	61.24	^[2]	From SMD-GIL
HBondAcidity (α)	0.275		Calculated using ^[4]
HBondBasicity (β)	0.070		Calculated using ^[4]
CarbonAromaticity	0.231		From stoichiometry
ElectronegativeHalogenicity	0.308		From stoichiometry
`eps=11.5 epsinf=2.04 HBondAcidity=0.275 HBondBasicity=0.070 SurfaceTensionAtInterface=61.24 CarbonAromaticity=0.231 ElectronegativeHalogenicity=0.308`

Example table

Name in Gaussian input file	Value	Reference	Comments/calculations
eps
epsinf
SurfaceTensionAtInterface
HBondAcidity (α)
HBondBasicity (β)
CarbonAromaticity
ElectronegativeHalogenicity
`eps= epsinf= SurfaceTensionAtInterface= HBondAcidity= HBondBasicity= CarbonAromaticity= ElectronegativeHalogenicity=`

References

↑ ^1.0 ^1.1 ^1.2 ^1.3 ^1.4 Marenich 2009 http://pubs.acs.org/doi/abs/10.1021/jp810292n
↑ ^2.00 ^2.01 ^2.02 ^2.03 ^2.04 ^2.05 ^2.06 ^2.07 ^2.08 ^2.09 ^2.10 ^2.11 ^2.12 Bernales 2012 http://pubs.acs.org/doi/abs/10.1021/jp304365v
↑ http://www.gaussian.com/g_tech/g_ur/k_scrf.htm
↑ ^4.0 ^4.1 ^4.2 http://www.huntresearchgroup.org.uk/research/research_il_alpha_beta_intro.html
↑ Daguenet 2006 http://pubs.acs.org/doi/abs/10.1021/jp0604903
↑ ^6.0 ^6.1 Huddleston 2001 http://pubs.rsc.org/en/Content/ArticleLanding/2001/GC/b103275p
↑ ^7.0 ^7.1 M. M. Huang, Y. P. Jiang, P. Sasisanker, G. W. Driver and H. Weingartner,  J. Chem. Eng. Data, 2011, 56, 1494–1499. http://pubs.acs.org/doi/abs/10.1021/je101184s
↑ Gonzalez 2012 http://pubs.acs.org/doi/abs/10.1021/je201334p
↑ ^9.0 ^9.1 G. Vakili-Nezhaad, M. Vatani, M. Asghari and I. Ashour, J. Chem. Thermodyn., 2012, 54, 148–154.
↑ ^10.0 ^10.1 ^10.2 G. Janz and M. Lorenz, J. Electrochem. Soc. 1961 volume 108, issue 11, 1052-1058 doi: 10.1149/1.2427946
↑ https://pubchem.ncbi.nlm.nih.gov/compound/sodium_carbonate#section=Spectral-Properties&fullscreen=true
↑ Weast, R.C. (ed.). Handbook of Chemistry and Physics. 60th ed. Boca Raton, Florida: CRC Press Inc., 1979., p. B-91
↑ http://cameo.mfa.org/wiki/Potassium_carbonate

[Marenich-1] 1.0 ^1.1 ^1.2 ^1.3 ^1.4 Marenich 2009 http://pubs.acs.org/doi/abs/10.1021/jp810292n

[Bernales-2] 2.00 ^2.01 ^2.02 ^2.03 ^2.04 ^2.05 ^2.06 ^2.07 ^2.08 ^2.09 ^2.10 ^2.11 ^2.12 Bernales 2012 http://pubs.acs.org/doi/abs/10.1021/jp304365v

[3] ttp://www.gaussian.com/g_tech/g_ur/k_scrf.htm

[abmethod-4] 4.0 ^4.1 ^4.2 http://www.huntresearchgroup.org.uk/research/research_il_alpha_beta_intro.html

[Daguenet-5] Daguenet 2006 http://pubs.acs.org/doi/abs/10.1021/jp0604903

[Huddleston-6] 6.0 ^6.1 Huddleston 2001 http://pubs.rsc.org/en/Content/ArticleLanding/2001/GC/b103275p

[Huang-7] 7.0 ^7.1 M. M. Huang, Y. P. Jiang, P. Sasisanker, G. W. Driver and H. Weingartner,  J. Chem. Eng. Data, 2011, 56, 1494–1499. http://pubs.acs.org/doi/abs/10.1021/je101184s

[Gonzalez-8] Gonzalez 2012 http://pubs.acs.org/doi/abs/10.1021/je201334p

[Vakili-9] 9.0 ^9.1 G. Vakili-Nezhaad, M. Vatani, M. Asghari and I. Ashour, J. Chem. Thermodyn., 2012, 54, 148–154.

[Janz-10] 10.0 ^10.1 ^10.2 G. Janz and M. Lorenz, J. Electrochem. Soc. 1961 volume 108, issue 11, 1052-1058 doi: 10.1149/1.2427946

[11] ttps://pubchem.ncbi.nlm.nih.gov/compound/sodium_carbonate#section=Spectral-Properties&fullscreen=true

[12] Weast, R.C. (ed.). Handbook of Chemistry and Physics. 60th ed. Boca Raton, Florida: CRC Press Inc., 1979., p. B-91

[13] ttp://cameo.mfa.org/wiki/Potassium_carbonate

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How to simulate a defined solvent environment

How to simulate a generic solvent environment

Solvent parameters

Notes on parameters

Types of SMD model for ILs

SMD input database

SMD-GIL

[C4C1Im][BF4]

[C4C1Im][PF6]

[C4C1Im][NTf2]

[C4C1Im][OTf]

[C4C1Im][SCN]

Molten salt [Li+,Na+,K+][CO32-]

Bismuth halometallate ionic liquid, parameterised for [C2C1Im][BiCl4]

Example table

References

[C₄C₁Im][BF₄]

[C₄C₁Im][PF₆]

[C₄C₁Im][NTf₂]

[C₄C₁Im][OTf]

[C₄C₁Im][SCN]

Molten salt [Li⁺,Na⁺,K⁺][CO₃^2-]

Bismuth halometallate ionic liquid, parameterised for [C₂C₁Im][BiCl₄]