TY - JOUR
T1 - Probing the Ion-Specific Effects at the Water/Air Interface and Water-Mediated Ion Pairing in Sodium Halide Solution with Ab Initio Molecular Dynamics
AU - Liu, Jinfeng
AU - Zhang, John Z.H.
AU - He, Xiao
N1 - Funding Information:
This work was supported by the National Key R&D Program of China (Grant No. 2016YFA0501700), National Natural Science Foundation of China (Grant Nos. 21703289, 21673074, 21761132022, 21433004, and 91753103), Shanghai Municipal Natural Science Foundation (Grant No. 18ZR1412600), Young Top-Notch Talent Support Program of Shanghai, NYU-ECNU Center for Computational Chemistry at NYU Shanghai, Innovation Program of Shanghai Municipal Education Commission (201701070005E00020), and NYU Global Seed Grant. We also thank the Supercomputer Center of East China Normal University for providing us computational time.
Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/11/8
Y1 - 2018/11/8
N2 - The ion-specific effects at the water/air interface represent a fundamentally essential topic of research, and high-level ab initio simulations are still demanding to reveal the microscopic picture of the interactions between ions and water at the solvation interface. In this work, we present a fragment-based ab initio molecular dynamics (AIMD) simulation of sodium halide solution droplet (in a neutral mixture of Na+, F-, Cl-, and Br- ions) at the MP2/aug-cc-pVDZ level. We show that the studied halide ions exhibit surface preference in the order (F- < Cl- < Br-) which is in accordance with the experimental observation. The resulting potential of mean force (PMF) for Br- produces a distinct minimum at the water/air interface, while the minimum of the PMF for F- appears in the bulk region. The ion-pairing interactions between halide anions and Na+ cations are characterized, and it reveals that the specific solvent-separated ion pairs (SIPs) are more preferred than the direct contact ion pairs (CIPs). The transition between different types of SIPs is observed. Other structural and dynamical properties of ions and ion-hydration shells are investigated. These results provide broader and new physical insights for understanding the ion-specific behavior in interfacial solvation at the atomistic level.
AB - The ion-specific effects at the water/air interface represent a fundamentally essential topic of research, and high-level ab initio simulations are still demanding to reveal the microscopic picture of the interactions between ions and water at the solvation interface. In this work, we present a fragment-based ab initio molecular dynamics (AIMD) simulation of sodium halide solution droplet (in a neutral mixture of Na+, F-, Cl-, and Br- ions) at the MP2/aug-cc-pVDZ level. We show that the studied halide ions exhibit surface preference in the order (F- < Cl- < Br-) which is in accordance with the experimental observation. The resulting potential of mean force (PMF) for Br- produces a distinct minimum at the water/air interface, while the minimum of the PMF for F- appears in the bulk region. The ion-pairing interactions between halide anions and Na+ cations are characterized, and it reveals that the specific solvent-separated ion pairs (SIPs) are more preferred than the direct contact ion pairs (CIPs). The transition between different types of SIPs is observed. Other structural and dynamical properties of ions and ion-hydration shells are investigated. These results provide broader and new physical insights for understanding the ion-specific behavior in interfacial solvation at the atomistic level.
UR - http://www.scopus.com/inward/record.url?scp=85056198542&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85056198542&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcb.8b09513
DO - 10.1021/acs.jpcb.8b09513
M3 - Article
C2 - 30351119
AN - SCOPUS:85056198542
SN - 1520-6106
VL - 122
SP - 10202
EP - 10209
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 44
ER -