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Abstract
We study a generic model of semiflexible polymer with self-interactions, which exhibits a multitude of structural phases. Previous studies employing canonical statistical analysis methods for the identification and characterization of these phases have been inconclusive as these approaches lead to inconsistent results for systems of finite size. In contrast, the recently introduced microcanonical inflection-point analysis method not only enables the systematic identification and classification of transitions but is also able to distinguish close transitions that standard canonical analysis cannot resolve. Extensive one- and two-dimensional replica-exchange Monte Carlo simulations were employed to obtain accurate estimates of the Boltzmann entropies for the microcanonical inflection-point analysis. Our study reveals a mixed structural phase dominated by hairpin and loop conformations that originates from a bifurcation of the collapse transition line known from flexible polymers. Canonical quantities such as specific heat or fluctuations of square radius of gyration do not signal any transition into this intermediate phase embraced by the well-known random-coil and toroidal phases. In addition, the formation of distinct versatile ground-state conformations including compact globules, rod-like bundles and toroids are observed from replica-exchange simulations, and validated by global optimization methods. By utilizing contact and distance maps, we systematically investigate the effect of the bending stiffness on ground-state conformations.