trappe-electrolyte

Extension of the TraPPE force field to carbonate electrolyte solvents

Molecule abbreviations

Abbreviation	Molecule
EC	Ethylene carbonate
PC	Propylene carbonate
DMC	Dimethyl carbonate
DEC	Diethyl carbonate
DME	Dimethoxyethane

Folder structure

forcefield

ffnonbonded.itp contains the mass and Lennard-Jones parameters of each atom type. The charges in this file are generally overwritten by the charges given in the molecule-specific itp files. ffbonded.itp contains parameters for bond, angle and dihedral interactions. Dihedrals use Gromacs type 3 (Ryckaert-Bellemans or OPLS form).

itp

This contains molecule-specific itp files, which specify the atom names, charges and bond connectivity for each molecule. Gromacs locates the parameters for the bonded interactions from ffbonded.itp (in the forcefield folder).

pdb

Files containing atom coordinates of each molecule. The order of the atoms in these files should match the corresponding itp files.

mdp

Gromacs molecular dynamics parameter (mdp) files. mdp_NPT_eq.mdp is for equilibration and will generate initial atom velocities and use the Berendsen barostat.

Atom type naming scheme

Tabulated parameters (WIP)

Bond lengths

Molecules	Bond	rb [nm]	Ref
EC, PC	O1=C2 (O=C)	0.120	[2]
EC, PC	C2-O3 (C-O)	0.136	[4]
EC, PC	O3-C5 (O-CH2)	0.143	[4]
EC	C5-C6 (CH2-CH2)	0.152	[4]
PC	O4-C6 (O-CH)	0.145
PC	C5-C6 (CH2-CH)	0.153
PC	C6-C7 (CH-CH3)	0.151

Note: Very similar bond types (e.g. EC CH₂-CH₂ and PC CH₂-CH) could be combined in a future release

Angles

Molecules	Angle	$\theta_0$	$k_\theta$ [kJ mol-1 rad-2]	Ref

Dihedrals

References

[1] J. Phys. Chem. B 2004, 108, 17596-17605 (TraPPE-6 ethers/glycols)

[2] J. Phys. Chem. B 2009, 113, 6415–6425 (TraPPE acrylate)

[3] J. Phys. Chem. B 2012, 116, 11234−11246 (TraPPE cyclic ether)

[4] J. Phys. Chem. B 2004, 108, 2016-2027 (Masia EC)