APPLE&P

APPLE&P is a polarizable forcefield suitable for many electrolytes and polymers.

To use the APPLE&P force field, you need a special license for APPLE&P that you can obtain from SCM.

APPLE&P use cases

APPLE&P has been specifically parametrized to the below list of molecules. For molecules not on the list, the force field may or may not be reasonable, and it is advised that you do your own testing.

Organic Molecules

  • alcohols

  • aldehydes

  • alkanes, alkenes, alkynes

  • amides

  • esters

  • ethers

  • imides

  • ketones

  • partially fluorinated alkanes

  • perfluoroalkanes

Energetic Materials

  • FOX-7

  • HMX

  • hydrazines

  • hydroxylammonium nitrate (HAN)

  • hydroxylethyl hydrazinium nitrate (HEHN)

  • PETN

  • RDX

  • TATB

  • TNT

Polymers

Note

The automatic atom typing may be very slow for large polymers containing the following functional groups: nitro, isocyanate groups, phenyl rings and conjugated rings with carbon and nitrogen (i.e. imidazole), amide, imide and azide groups, as well as phosphorous groups with multiple oxygen atoms (phosphorous oxoacids and derivatives).

  • polyimides

  • polyamides

  • polyesters

  • polyethers (e.g., PEO)

  • PIB

  • PDMS

  • PTFE

  • polybutadiene

  • polyalkanes

Solvents/Additives

  • acetone

  • alcohols

  • cyclic carbonates (e.g., ethylene carbonate)

  • ethers (e.g., dimethoxyethane)

  • linear carbonates (e.g., dimethyl carbonate)

  • nitriles (e.g., acetonitrile, succinonitrile, adiponitrile)

  • partially fluorinated carbonates (e.g., FEC)

  • partially fluorinated ethers

  • perfluoroethers

  • sulfones (cyclic and acyclic)

  • water

SEI compounds

  • dilithium dicarbonates

  • lithium carbonates

  • LiF

  • Li₂CO₃

Cations

  • ammoniums

  • H₃O⁺, hydronium

  • hydraziniums

  • imidazoliums

  • K⁺, potassium

  • Li⁺, lithium

  • Mg²⁺, magnesium

  • morpholiniums

  • Na⁺, sodium

  • piperidiniums

  • pyrrolidiniums

  • Zn²⁺, zinc

Anions

  • B(CN)₄⁻, tetracyanoborate

  • BF₄⁻, tetrafluoroborate

  • BF₃CF₃⁻, CF₃BF₃⁻, trifluoro(trifluoromethyl)borate

  • BF₃CH₃⁻, CH₃BF₃⁻, methyltrifluoroborate

  • BOB, bis(oxalate)borate

  • C(CN)₃⁻, tricyanomethanide

  • CN⁻, cyanide

  • CN₇⁻, azidotetrazolate

  • CO₃²⁻, carbonate

  • F⁻, fluoride

  • FSI, bis(fluorosulfonyl)imide

  • N₃⁻, azide

  • N(CN)₂⁻, dicyanamide

  • NO₃⁻, nitrate

  • OH⁻, hydroxide

  • PF₆⁻, hexafluorophosphate

  • SO₃CF₃⁻, triflate

  • TFSI, bistriflimide

Electrodes

  • graphite

  • iridium

APPLE&P potential shapes

In general, APPLE&P uses similar expressions for the potentials, with some differences. For completeness’ sake we list all APPLE&P potentials below.

See also

Potential shapes force other force fields.

  • Bond: the same as the stretch potential above.

\[V^\text{bond} = \frac{1}{2} f_c (r-r_0)^2\]

  • Bend: the same as the harmonic angle potential above.

\[V^\text{bend} = \frac{1}{2} f_c (\phi-\phi_0)^2\]

  • Torsion: cyclic.

\[V^\text{torsion} = - \sum_{m=1}^n c_m \cos(m \phi)\]

  • Out-of-plane angle: sum of three harmonic terms, each corresponding to an angle between the Rij bond and the (jkl) plane, where j is the central atom and i, k, l are permutations of the other three atoms.

\[V^\text{oop} = \frac{1}{2} f_c (\phi_1^2 + \phi_2^2 + \phi_3^2)\]

  • Dispersion: mix of the Buckingham and Lennard-Jones potentials.

\[V^\text{dispersion} = A e^{-Br} - \frac{C}{r^6} + \frac{D}{r^{12}}\]

  • Electrostatic potential: charge-charge, charge-dipole and dipole-dipole. Interaction are excluded for the 1-2 and 1-3 neighbors and can be scaled for the 1-4 ones. For each atom, the self-consistent induced dipole moment is computed from its polarizability and the electric field due to other charges and dipoles. The latter includes the Thole damping.

\[V^\text{elstat} = \sum_{i>j} {} \frac{q_i q_j}{4 \pi \epsilon_0 r_{ij}} + \sum_{i} {} \vec{\mu_i} \cdot \vec{E_i}\]

APPLE&P Python functions

The scm.appleandp Python module contains the below functions.

For example usage, see the APPLE&P tutorial

appleandp_packmol(molecules, forcefield_file, **kwargs)[source]
molecules: list of Molecule

If they are ions they should have the molecule.properties.charge set to the charge

forcefield_file: str

The force field file will be written here. It will be overwritten if it already exists

**kwargs: various options

See the documentation for the packmol() function

Returns: a PLAMS Molecule created with packmol

This function differs from the PLAMS implementation of packmol in that it also writes out a force field file for use with APPLE&P.