Van der Waals Effects on semiconductor clusters.
Van der Waals (vdW) interactions play an important role on semiconductors in nanoscale. Here, we utilized first-principles calculations based on density functional theory to demonstrate the growth mode transition from prolate to multiunit configurations for Gen (n = 10-50) clusters. In agreement with the injected ion drift tube techniques that "clusters with n < 70 can be thought of as loosely bound assemblies of small strongly bound fragments (such as Ge7 and Ge10 )," we found these stable fragments are connected by Ge6 , Ge9 , or Ge10 unit (from bulk diamond), via strong covalent bonds. Our calculated cations usually fragment to Ge7 and Ge10 clusters, in accordance with the experiment results that the spectra Ge7 and Ge10 correspond to the mass abundance spectra. By controlling a germanium cluster with vdW interactions parameters in the program or not, we found that the vdW effects strengthen the covalent bond from different units more strikingly than that in a single unit. With more bonds between units than the threadlike structures, the multiunit structures have larger vdW energies, explaining why the isolated nanowires are harder to produce. © 2015 Wiley Periodicals, Inc.
School of Physics and Engineering, Henan University of Science and Technology, Luoyang City, Henan Province, 471023, China.|Center for Clean Energy and Quantum Structures, and School of Physics and Engineering, Zhengzhou University, Zhengzhou, 450001, China.
Haisheng
H
Li
Center for Clean Energy and Quantum Structures, and School of Physics and Engineering, Zhengzhou University, Zhengzhou, 450001, China.|Department of Physics and Electronic Science, Zhengzhou Normal University, Zhengzhou, 450044, China.
Weiguang
W
Chen
Department of Chemistry, University College London, London, WCIH 0AJ, United Kingdom.
Xiaoyu
X
Han
School of Physics and Engineering, Henan University of Science and Technology, Luoyang City, Henan Province, 471023, China.
Liben
L
Li
Center for Clean Energy and Quantum Structures, and School of Physics and Engineering, Zhengzhou University, Zhengzhou, 450001, China.
Qiang
Q
Sun
Department of Chemistry, University College London, London, WCIH 0AJ, United Kingdom.
Zhengxiao
Z
Guo
Center for Clean Energy and Quantum Structures, and School of Physics and Engineering, Zhengzhou University, Zhengzhou, 450001, China.
Yu
Y
Jia
PBE-TS+SCS; Van der Waals interactions; covalent bond; first-principles calculations; germanium cluster