Molecular simulation for flexibility of a single clay layer

Hisako Sato, Akihiko Yamagishi, Katsuyuki Kawamura

Research output: Contribution to journalArticlepeer-review

70 Citations (Scopus)

Abstract

Molecular dynamics (MD) simulations have been performed to study the flexibility of smectite clay minerals. We aim at the quantitative understanding of the mechanical behavior of a single clay layer in a completely exfoliated state. The repeating unit of a clay layer is taken to be ao = 0.52 nm and bo = 0.902 nm with formula of 2Na1/3 Al2[Si11/3Al1/3]O10(OH)2 which corresponds to that of beidellite. When the size of the basic cell (A = 9.3 nm, B = 2.6 nm, and C = 5 nm) (denoted by A-type cell) is reduced by 3-40% in the A-direction, the stationary structure of a clay layer is obtained as a curved sheet with a 2:1 smectite-type layer structure. In such a curved state, the layer experiences a stress of 0.5-0.7 GPa. The layer structure of a clay fractures when the size of the same basic cell is reduced by more than 40%. The bending constant is estimated for a curved layer by plotting the inverse of the average radius against stress. The similar calculations are performed by reducing the size of the basic cell (A = 3.1 nm, B = 10.7 nm, and C = 5 nm) (denoted by B-type cell) in the B-direction. The clay layer is found to be more flexible along the A-axis direction than along the B-axis direction. When the microscopic structure of a curved clay layer is examined, it is concluded that the main origin of flexibility lies in the change of Si-O-Si angles in the silicate tetrahedral sheets rather than in the change of bond lengths.

Original languageEnglish
Pages (from-to)7990-7997
Number of pages8
JournalJournal of Physical Chemistry B
Volume105
Issue number33
DOIs
Publication statusPublished - Aug 23 2001

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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