Four- and eight-membered rings carbon nanotubes:A new class of carbon nanomaterials

•A new allotrope of carbon nanotubes (CNTs) composed of alternating four- and eight-membered rings is simulated and calculated in theory.•The analysis of the average binding energy shows that the stability of these CNTs will increase with the diameter increasing.•The electronic properties of these CNTs are independent of their diameter, number of walls and chirality, exhibit obvious metal properties.