The saturated vapor pressures of 4 nonaromatic bicyclic 1,3-thiazine and 1,3-selenazine derivatives have been measured by the method of transpiration by inert gas-carrier in the temperature range of 308-392 K. Based on the experimental data the thermodynamic functions of sublimation have been calculated. The sublimation enthalpies of the compounds vary from 104 to 150 kJ mol(-1) depending on the chemical nature of the substituent in the aryl moiety and the heteroatom in the bicyclic fragment. The crystal lattice energy of thiazines decreases with the introduction of substituents in the following order: cyano > acetyl > isopropyl. New approach has been suggested to evaluating sublimation enthalpy of the studied and structurally related compounds by using clusterization of the space of experimental points.