Molecular dynamics model for nano-motions of FePd nanohelices

• Published in: Journal of applied physics 2017-04, Vol.121 (15)
• Main Authors: Taya, M., Xu, C., Matsuse, T., Muraishi, S.
• Format: Article
• Language: English
• Subjects: Applied physics; Computer simulation; Ferrous alloys; Intermetallic compounds; Iron compounds; Magnetic fields; Magnetic moments; Magnetism; Martensitic transformations; Molecular dynamics; Palladium compounds; Phase transitions; Shape memory alloys; Shrinkage
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4979474

Shrinkage and relaxation motions of flexible FePd nanohelices of FePd nanorobots are simulated by a molecular dynamics (MD) model where FePd is a paramagnetic shape memory alloy that can exhibit phase transformation accompanied by softening of the nanohelix under an applied magnetic field (H-field). Two designs of FePd nanorobots are used: (i) a FePd cylindrical head connected to a FePd nanohelix tail and (ii) a FePd nanohelix alone. The geometry and dimensions of the FePd robots are taken after the as-processed FePd nanorobots. In the MD simulation, the FePd head and nanohelix are divided into a number of segmented FePd spheres, each having its magnetic moment. The results of the MD model reveal that upon the applied constant magnetic field, the initial gaps (g = 3 nm) between the adjacent turns of the FePd nanohelix are closed, resulting in the total shrinkage (Stot) of 47 nm of the FePd nanorobot. The effects of the applied H-field on Stot are examined by using the MD model and the M-H curve of FePd fitted with Langevin type, resulting in the smaller applied magnetic field leading to the smaller Stot. The results of the MD model provide us with an effective tool in the analysis and design of new nanorobots based on the paramagnetic shape memory alloy of FePd nanohelices that can exert dynamic vibrations on target cells under the oscillating magnetic field.