The stability of ice I cubic (ice I-c) whose voids are occupied by neon particles is investigated using a hybrid type of isobaric grand-canonical Monte Carlo simulation. We show that the resulting neon hydrate is stable under high pressure and temperature where ice I-c alone is unstable, suggesting the existence of a novel neon hydrate of ice I-c. We also show through chemical potential calculation that the neon hydrate of the ice I-c structure is more favorable than the neon hydrate of the ice II structure, whose existence was proven from experiment under high pressure condition. (C) 2009 Elsevier B.V. All rights reserved.