# Create a box of TIP3P water with a hole for a Na+ ion in the center.

# Load AMBER '96 forcefield for protein.
source leaprc.ff96

# Create a container with a single sodium ion.
system = sequence { Na+ }

# Solvate in water box.
solvateBox system TIP3PBOX 10.0 iso

# Remove ion.
remove system system.1

# Check sytem.
check system

# Write parameters.
saveAmberParm system system-central.prmtop system-central.crd

# Exit
quit