Farkaš Barbara, de Leeuw Nora H
School of Chemistry, Cardiff University, Cardiff, CF10 3AT, United Kingdom.
Nanotechnology. 2020 May 8;31(19):195711. doi: 10.1088/1361-6528/ab6fe0.
Cobalt nanoparticles with diameters of 8 nm have recently shown promising performance for biomedical applications. However, it is still unclear how the shape of cobalt clusters changes with size when reaching the nanoparticle range. In the present work, density functional theory calculations have been employed to compare the stabilities of two non-crystalline (icosahedron and decahedron) shapes, and three crystalline motifs (hcp, fcc, and bcc) for magic numbered cobalt clusters with up to 1500 atoms, based on the changes in the cohesive energies, coordination numbers, and nearest-neighbour distances arising from varying geometries. Obtained trends were extrapolated to a 10 size range, and an icosahedral shape was predicted for clusters up to 5500 atoms. Larger sized clusters adopt hcp stacking, in correspondence with the bulk phase. To explain the crystalline/non-crystalline crossovers, the contributions of the elastic strain density and twin boundary from the specimen surfaces to the cohesive energy of different motifs were evaluated. These results are expected to aid the design and synthesis of cobalt nanoparticles for applications ranging from catalysis to biomedical treatments.
直径为8纳米的钴纳米颗粒最近在生物医学应用中展现出了良好的性能。然而，当钴团簇尺寸达到纳米颗粒范围时，其形状如何随尺寸变化仍不清楚。在本工作中，基于不同几何结构引起的结合能、配位数和最近邻距离的变化，采用密度泛函理论计算，比较了原子数高达1500的幻数钴团簇的两种非晶形状（二十面体和十面体）以及三种晶体结构（六方密堆积、面心立方和体心立方）的稳定性。将得到的趋势外推到10倍的尺寸范围，预测原子数高达5500的团簇为二十面体形状。更大尺寸的团簇采用六方密堆积结构，与体相一致。为了解释晶体/非晶体的转变，评估了试样表面的弹性应变密度和孪晶界对不同结构结合能的贡献。这些结果有望有助于钴纳米颗粒的设计和合成，其应用范围涵盖从催化到生物医学治疗等领域。
