Table 1. Chemical Compounds Used for Molecular Simulation in This Work^a.

chemical name	chemical formula	CAS number	force field
water	H2O	7732-18-5	TIP3P100
water	H2O	7732-18-5	modified TIP4P (this work)
hydrogen	H2	1333-74-0	Marx99
hydrogen	H2	1333-74-0	Vrabec102
hydrogen	H2	1333-74-0	Cracknell97
hydrogen	H2	1333-74-0	Hirschfelder107
hydrogen	H2	1333-74-0	Buch106

^aFor direct computation of chemical potentials, improving the efficiency, and calculating the solubilites, fractional molecules are used. Interaction parameters of the modified TIP4P force field are provided in the Supporting Information (SI). Mixture compositions of water−hydrogen systems are explicitly provided for every temperature and pressure in Table 2.