The ability of block copolymers to spontaneously self-assemble into a variety of ordered nano-structures not only makes them a scientifically interesting system for the investigation of order-disorder phase transitions, but also offers a wide range of nano-technological applications. The architecture of a diblock is the most simple among the block copolymer systems, hence it is often used as a model system in both experiment and theory. We introduce a new soft-tetramer model for efficient computer simulations of diblock copolymer melts. The simplicity of the model allows to scan the control parameter space in a completeness that has not been reached in previous molecular simulations. We develop a novel method for the identification of the observed diblock copolymer mesophases that formalizes the usual approach of direct visual observation, using the characteristic geometry of the structures.