Something is off with lopes.xml

[mattwthompson]

Some validation runs of EMIM-Tf2N have produced densities lower than the authors reported. The non-bonded parameters are probably most important but various bonded terms probably also have an impact.

Currently I see no better way to verify parameters than elbow grease.

This also points to the general issue: we probably need a better way to validate from-scratch xml files vs reported properties in relevant paper(s).

[mattwthompson]

Density appears to be fixed (f0462ae or more cleanly f0462ae) but we should probably find a more robust way of verifying that forcefield parameters are copied accurately from paper(s).

See NPT simulations below, various Lopes papers (i.e. Table 5 in this one), and some numbers I threw together from NIST

Cation	Anion	MW (amu)	Density (kg/m^3)	Density (nm^-3)	L (nm) if 400 pairs
EMIM	Tf2N	391.31	1,514.00	2.33	5.56
EMIM	OTf	260.23	1,370.20	3.17	5.02
BMIM	Tf2N	419.36	1,432.00	2.06	5.79
BMIM	OTf	288.29	1,296.60	2.71	5.29
HMIM	Tf2N	447.42	1,372.40	1.85	6.00
HMIM	OTf	316.34	1,234.90	2.35	5.54

[mattwthompson]

Closing because after #2 the behavior and properties of systems atomtyped with this force field are reasonable and stable.