The equilibrium crystal structure of a beta-quinol clathrate occupied by various gases is determined through empirical force field calculations. The guests with van der Waals volume V-m less than or equal to 27 cm(3)/mol affect the structure and rigidity of the lattice in a manner independent of their chemical nature : The guest-host attraction leads to a shrinking of the host cages. On the other hand, the inclusion of molecules of the volume 27 cm(3)/mol less than or equal to V-m less than or equal to 46 cm(3)/mol expands the cages. Guest molecules render the host lattice more rigid, except for large spherical rotor type molecules, which soften the lattice, eventually destroying it. The inclusion of molecules with V-m>46 cm(3)/mol is likely to be impossible. The energy of clathrate formation increases with increasing V-m, with the polar guests forming more stable clathrates than the nonpolar ones with the same V-m. interestingly, the optimal guest-cage compatibility occurs when the volume of guest molecules differs by less than 50%, from the volume of the empty cage. The orientation of a guest molecule in a cage is mainly determined by a competition of three types of interactions. (i) Van der Waals interactions tend to direct the long axis of the guests along the c-axis of the cage. (ii) The electrostatic guest-host interaction tends to place a positively charged guest atom into the center of the cage. (iii) Electrostatic guest-guest interactions tend to align the dipole moments of the included molecules along the c-axis. The different orientations are rationalized in terms of the complementary influences of the guest size, guest polarity and an "atomic size" factor. The calculated barriers hindering the reorientation movement of guest molecules in a cage are found to be in a qualitative agreement with experimental data except for the N-2 and CO molecules, which are supposed to be considerably polarized by the cage. The C-3-reorientation motion of ethane is predicted to be accompanied by its synchronous rotation around the C-C bond.