Temperature (left column), hydrogen density (middle column), and ionization fraction n_e⁻/n_H (right column) of the gas predicted by CLOUDY as functions of the visual extinction A_V and the X-ray radiation field scaling factor G_X (top row), the turbulent velocity dispersion v_tur (middle row), and the metallicity Z (bottom row). Nonvarying parameters are set to their standard values. In particular, the total pressure of the gas is set to 10^6.5 K cm⁻³, G_X = 10 (for middle and bottom rows), v_tur = 10 km s⁻¹ (for top and bottom rows), and Z = Z_⊙ (for top and middle rows). The black curves correspond to isocontours. The transition from ionized to atomic phase and that from atomic to molecular are defined by n_e⁻/n_H⁰ = 1 and n_H⁰/n_H2 = 1, respectively, indicated with a blue curve. The blue I, A, and M identify the different gas phases: ionized, atomic, and molecular, respectively.