  In this work we have employed density-functional theory with hybrid
functionals to investigate the atomic and electronic structure of bare and
hydrogenated Mn doped ZnO nanowires with small diameter. We determine changes
in magnetic and electronic structure of Mn-doped ZnO nanowires due to surface
effects, such as hydrogen adsorption on the surface, presence of oxygen
vacancies and dangling bonds. In the absence of passivation on the nanowire
surface, the manganese atoms segregate to the surface, whereas under hydrogen
adsorption the incorporation of Mn is energetically more favourable at inner
sites. The presence of additional oxygen vacancies does not produce signficant
changes in magnetic moments, although it produce significant changes in charge
localization.
