Table 2. Atom Types and Point Charge Assignments for the PolCA Organosilicate Force Fielda.
| atom type | description | q |
|---|---|---|
| -CHx-Si-(CHx)3 | Any alkyl group connected to Si in an alkysilane molecule | –0.24 |
| CH3-Si-O- | CH3 group connected to Si in a silanol, alkoxysilane, or siloxane molecule | –0.32 |
| -CH2-Si-O- | CH2 group connected to Si in a silanol, alkoxysilane, or siloxane molecule | –0.27 |
| -Si-OC-CHx- | Any alkyl group connected to an alkoxysilane oxygen | +0.25 |
| -Si-OC-CHx- | Alkoxysilane oxygen | –0.68 |
| -Si-OH-H | Silanol oxygen | –0.88 |
| -Si-OH-H | Silanol hydrogen | +0.44 |
| -Si-OB-Si- | Siloxane “bridging” oxygen | –0.88 |
| -Si- | Tetrahedrally substituted silicon | bespoke |
a
The atom type in question is shown in bold. The silicon charges for each molecule are calculated after assigning all other charges by enforcing the charge neutrality constraint.