We study the pressure dependence of the melting mechanism of a surface free Lennard-Jones crystal by constant pressure Monte Carlo simulation. The difference between the overheating temperature(T_OH) and the thermodynamical melting point(T_M) increase for increasing pressure. When particles move into the repulsive part of the potential the properties at T_OH change. There is a crossover pressure where the volume jump becomes pressure-independent. The overheating limit is pre-announced by

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... excitation of big clusters of defects. The temperature zone where the system is dominated by these big clusters of defects increases with increasing pressure. Beyond the crossover pressure we find that excitation of defects and clusters of them start at the same temperature scale related with T_OH.