Formation of icosahedral nanowires

Abstract

An icosahedral nanowire (INW) is a one‐dimensional structure where a single atom and a five‐membered ring are alternating to form a −1−5−1−5−1− stacking. The 1−5−1−5−1 segment of this stacking forms an icosahedron and constitutes the unit cell of an INW. In molecular dynamics (MD) simulations of stretching of metal nanowires (NWs), INWs are frequently formed at their deformation necks. Previous simulations found that the formation of INWs is more favored for thin NWs than thick NWs. To closely investigate this size dependence of INW formation, we have carried out stretching simulations of Mg NWs and examined the creation of icosahedral arrangement of atoms at their deformation necks. Our results show that thin NWs tend to produce slender necks, the atoms of which first become disordered and then rearrange themselves into an icosahedral arrangement. Thick nanowires rarely form such slender necks and this accounts for their low yield of INWs. We have also investigated a continuous and bond‐conserving process that converts the HCP arrangement of atoms into an icosahedral one. We found that the nearest‐neighbor bonds are not conserved and only a small fraction of nearest‐neighbor atoms in an icosahedral unit cell are initially nearest neighbors.

Formation of pentagonal atomic chains in BCC Fe nanowires

“…It is important to point out that the pentagonal atomic chains are not formed at low temperatures of 10 and 100 K as well as nanowire size larger than 2.83 nm. The observed formation of pentagonal atomic chains promoted by small nanowire size and higher temperatures is in agreement with those reported for FCC and HCP nanowires [11][12][13][14][15][16][17][18] . In addition to above, it has been shown that the crystallographic orientation and strain rate influence the formation of pentagonal atomic chains during tensile deformation in FCC nanowires [12][13][14] .…”

“…In agreement with experimental observations, many atomistic simulation studies have also shown the formation of pentagonal atomic chains in Cu [11][12][13] , Al 13 , Ni 13,14 , and Au 15,16 . The pentagonal structures have also been observed in HCP Mg nanowires during the atomistic simulations studies 17,18 . The evidence of pentagonal structures has been found during the stretching of BCC Na nanowires using first-principles molecular dynamics simulations 19 [19].…”

“…based on the Arrhenius model 9 . Further, the observation of transition temperature as a function of size in BCC Fe nanowires appears to be significant, since there is no such transition temperature established yet in either FCC [11][12][13][14][15][16] or HCP nanowires 17,18 . These results indicates that at proper size and temperature, the BCC Fe nanowires can also exhibit long pentagonal atomic chains during the deformation.…”