Abstract
| Original language | English |
|---|---|
| Pages (from-to) | 197-211 |
| Journal | Clay Minerals |
| Volume | 51 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - 2016 |
| MoE publication type | A1 Journal article-refereed |
Fingerprint
Keywords
- molecular dynamics
- density functional theory
- layer charge
- montmorillonite
- swelling
- diffusion
Cite this
}
Effect of layer charge on the crystalline swelling of Na+, K+ and Ca2+ montmorillonites: DFT and molecular dynamics studies. / Seppälä, Anniina (Corresponding Author); Puhakka, Eini; Olin, Markus.
In: Clay Minerals, Vol. 51, No. 2, 2016, p. 197-211.Research output: Contribution to journal › Article › Scientific › peer-review
TY - JOUR
T1 - Effect of layer charge on the crystalline swelling of Na+, K+ and Ca2+ montmorillonites: DFT and molecular dynamics studies
AU - Seppälä, Anniina
AU - Puhakka, Eini
AU - Olin, Markus
PY - 2016
Y1 - 2016
N2 - The swelling and cation exchange properties of montmorillonite are fundamental in a wide range of applications ranging from nanocomposites to catalytic cracking of hydrocarbons. The swelling results from several factors and, though widely studied, information on the effects of a single factor at a time is lacking. In this study, density functional theory (DFT) calculations were used to obtain atomic-level information on the swelling of montmorillonite. Molecular dynamics (MD) was used to investigate the swelling properties of montmorillonites with different layer charges and interlayer cationic compositions. Molecular dynamics calculations, with CLAYFF force field, consider three layer charges (-1.0, -0.66 and -0.5 e per unit cell) arising from octahedral substitutions and interlayer counterions of Na, K and Ca. The swelling curves obtained showed that smaller layer charge results in greater swelling but the type of the interlayer cation also has an effect. The DFT calculations were also seen to predict larger d values than MD. The formation of 1, 2 and 3 water molecular layers in the interlayer spaces was observed. Finally, the data from MD calculations were used to predict the self-diffusion coefficients of interlayer water and cations in different montmorillonites and in general the coefficient increased with increasing water content and with decreasing layer charge.
AB - The swelling and cation exchange properties of montmorillonite are fundamental in a wide range of applications ranging from nanocomposites to catalytic cracking of hydrocarbons. The swelling results from several factors and, though widely studied, information on the effects of a single factor at a time is lacking. In this study, density functional theory (DFT) calculations were used to obtain atomic-level information on the swelling of montmorillonite. Molecular dynamics (MD) was used to investigate the swelling properties of montmorillonites with different layer charges and interlayer cationic compositions. Molecular dynamics calculations, with CLAYFF force field, consider three layer charges (-1.0, -0.66 and -0.5 e per unit cell) arising from octahedral substitutions and interlayer counterions of Na, K and Ca. The swelling curves obtained showed that smaller layer charge results in greater swelling but the type of the interlayer cation also has an effect. The DFT calculations were also seen to predict larger d values than MD. The formation of 1, 2 and 3 water molecular layers in the interlayer spaces was observed. Finally, the data from MD calculations were used to predict the self-diffusion coefficients of interlayer water and cations in different montmorillonites and in general the coefficient increased with increasing water content and with decreasing layer charge.
KW - molecular dynamics
KW - density functional theory
KW - layer charge
KW - montmorillonite
KW - swelling
KW - diffusion
U2 - 10.1180/claymin.2016.051.2.07
DO - 10.1180/claymin.2016.051.2.07
M3 - Article
VL - 51
SP - 197
EP - 211
JO - Clay Minerals
JF - Clay Minerals
SN - 0009-8558
IS - 2
ER -