SPICA: Surface Property fItting Coarse grAined model

Force Field

tSPICA Force Field

Tutorial for generating tSPICA parameters

tSPICA is an extension of SPICA designed for temperature (T ) and pressure (P ) dependence. Details of the SPICA FF can be found here. The full details of tSPICA can be found in the publication here. tSPICA scales the Lennard-Jones parameter εij for the interacting pair of bead type i and j as a function of T and P with

εij (T,P ) = εij,SPICA + (a1,ij )ΔP Δεij,T + (a2,ij )ΔT Δεij,P


εij,SPICA = SPICA εij at 303 K and 0.1 MPa
ΔP = (P - P0) / P0   P0 = 0.1 MPa
ΔT = (T - T0) / T0   T0 = 303 K
Δεij,T = ε1,ij ΔT + ε2,ijT )2
Δεij,P = ε3,ij ΔP + ε4,ijP )2
ε1,ij and ε2,ij are the temperature dependent coefficients
ε3,ij and ε4,ij are the pressure dependent coefficients
a1,ij and a2,ij are the cross coefficients, required when T != 303 K and P != 0.1 MPa

The coefficients are fit to experimental data (typically density and surface tension). Applying this small correction improves the transferability of the original SPICA force field for non-ambient T and P conditions. All other details of the SPICA FF remain the same.

SPICA Force Field

Research Institute for Interdisciplinary Science (RIIS)
Okayama University