A new force field for the molecular modeling of ionic liquids of the dialkylimidazolium cation family based on the OPLS-AA/AMBER framework is presented and discussed. Ab initio calculations were performed to obtain several terms in the force field not yet defined in the literature. These include torsion energy profiles and distributions of atomic charges that blend smoothly with the OPLS-AA specification for alkyl chains. Validation was carried out comparing simulated and experimental data on fourteen different salts, comprising three types of anion and five lengths of alkyl chain, both in the crystalline and liquid phases. The present model can be regarded as a step towards a general force field for ionic liquids of the imidazolium cation family that was built in a systematic way, is easily integrated with OPLS-AA/AMBER and is transferable between different combinations of cation-anion.