Is it possible that in open systems can occur phase transitions if the required conditions (i.e., temperature and pressure) are met? Are there examples?
Some examples are found, e.g., in the 1978 paper Experimental Studies of Some Phase Transitions in Nonequilibrium Open Systems (namely, "onset of self-sustained electric oscillation, evolution of vortex around a sink hole and successive transitions in liquid crystals due to an electric field").
And not only phase transitions can take place in open systems, also critical states can be sustained, e.g., in systems displaying Self-Organized Criticality, such as a sand pile over which grains fall randomly.
Often open systems can be described as nonlinear dynamical systems so the formalism of chaos theory can be applied. In closed system a phase transition, that occurs above a critical point, requires equilibrium conditions.
In open systems ( nonlinear dynamical systems ) a critical point is generalized into a bifurcation point. As in open systems also critical points resp. bifurcation points exist, phase transitions can also occur in open systems :
Collections of identical atoms can behave in macroscopically different ways when their temperature and density are changed. For example, water exists as a gas, a liquid and a solid at different temperatures. Why? These "phases" are collective effects that emerge under equilibrium conditions. The changes, called "phase transitions", are a big object of study in Physics. Changes of temperature in the early universe at which new collective modes of motion emerged, like the symmetry breaking in the standard model, are also usually called phase transitions. Closed systems typically quickly reach thermodynamic equilibrium, after which nothing changes. Equilibrium can usually be assumed if the external conditions on a closed system are changed slowly enough. Open systems, on the other hand, are generally under non-equilibrium conditions.
The distinction between open and closed systems in crucial to the Second Law because open systems do not have to have increasing entropy. The Earth is an open system: it receives energy from the sun and exports an equal amount of energy to the cold night sky. The whole biosphere copiously produces entropy all the time, but this does not mean that the entropy of the biosphere must increase, because it is not open. For a more technical discussion, see here. (Many foolish people believe that biological evolution contradicts the Second Law --- there are many web pages about this -- but this is completely incorrect).
The Ising model of a magnetic phase transition. Here we see how a new ordered structure can spontaneously emerge as some external parameter (here the temperature) is varied continuously. The transition point, often called a critical point, is sharp and the new phase can appear continuously or discontinuously at that "tipping point". At lot has been written about such points, including much nonsense.
Near a critical point, fluctuations can become very large as the system becomes "soft" at the transition.
Such points are more generally called bifurcation points and they can occur in non-equilibrium systems as well, and can lead to the sudden appearance of new states of motion or even spatial patterns. A good example is the onset of period 2 in the logistic map. Pattern formation is the study of such non-equilibrium structures.