  NPzzT and MuPzzT simulations of K-montmorillonite hydrates were performed
employing hybrid Monte Carlo simulations. Two condition sets were studied, P=1
atm and T= 300 K (ground level conditions), and P=600 atm and T= 394 K; this
last condition mimics a burial depth close to 4 km. For these conditions,
swelling curves as a function of the reservoir water vapor pressure were built.
We found the single layer K-montmorillonite hydrate stable for high vapor
pressures for both, burial and ground level conditions. A simple explanation
for this high stability is given.
