TABLE 5.
Summary of Drude Polarizable and CHARMM NMA Gas-Phase Dimer Interaction Energies for Heterodimers of NMA with Water and an NMA–NMA Homodimera
| properties | experiment/QM kcal/mol | CHARMM kcal/mol | Drude (unscaled/vthole) kcal/mol | Drude (scaled/vthole) kcal/mol |
|---|---|---|---|---|
| Emin (NMA–water: conf1) | –5.3 | –6.6 | –5.5 | –5.6 |
| Emin (NMA–water: conf2) | –6.3 | –6.2 | –6.3 | –6.5 |
| Emin (NMA–water: conf3) | –4.7 | –6.4 | –5.0 | –4.7 |
| Emin (NMA–NMA: dimer) | –6.8 | –7.8 | –7.0 | –6.6 |
a
The Drude model corresponds to the optimal choice of LJ parameters from the unscaled/vthole class of electrostatic models. The TIP3P95 and SWM4-NDP20 water models are used to accompany the CHARMM and Drude NMA models, respectively. Models are compared to QM calculations at the MP2/6-311+G(3df,2p) level, including a basis set superposition correction. The energies correspond to the minimum along the radial coordinate illustrated in Figure 2.