Chemical trends in structure and magnetism of bimetallic nanoparticles from atomistic calculations
By means of large scale first-principles calculations in the framework of density functional theory, structure and magnetism of 561 atom nanoparticles are compared in order to obtain a systematic picture of the evolution with respect to a change in the constitutional elements. The investigation comprises ordered and disordered, cuboctahedral, icosahedral and decahedral morphologies of composition A265B296, where A is one of Mn, Fe and Co and B is Pt and, additionally, with A = Fe and B = Ni, Pd, Pt, Ir and Au. Fe–Ir and Fe–Pd and Co–Pt exhibit in comparison with Fe–Pt an increased tendency to form multiply-twinned structures and prefer segregation of the heavier element to the surface. The latter trend also applies to Fe–Au, where, on the other hand, icosahedral and crystalline motifs are very close in energy. Only in Mn–Pt the formation of multiply-twinned structures is effectively suppressed. The combinations with reduced valence electron concentration, Mn–Pt and Fe–Ir, exhibit a strong preference for antiferromagnetic spin order. The structural and magnetic trends are tentatively related to the change in features in the element and site-resolved electronic density of states.
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