TY - JOUR
T1 - Ab initio metadynamics simulations on the formation of calcium silicate aqua complexes prior to the nuleation of calcium silicate hydrate
AU - Li, Yunjian
AU - Pan, Hui
AU - Li, Zongjin
N1 - Publisher Copyright:
© 2022 Elsevier Ltd
PY - 2022/6
Y1 - 2022/6
N2 - Although the calcium silicate hydrate (C-S-H) has been used for millennium, the structure and formation of C-S-H are still unclear at atomistic level. In this work, we find two kinds of calcium silicate aqua complexes, [Ca(H2O)n(SiO2(OH)2)] and [Ca(H2O)n(SiO(OH)3)]+, prior to the nuleation of C-S-H. The ab initio metadynamics simulations show that [Ca(H2O)n(SiO2(OH)2)] and [Ca(H2O)n(SiO(OH)3)]+ have six and five stable states on the free energy surface (FES), respectively. There are different ligand substitution mechanisms between the FES minima. The four- and six- coordinated [Ca(H2O)n(SiO2(OH)2)] only follow associative and dissociative mechanisms, respectively. While both dissociative and associative mechanisms apply to the six-coordinated [Ca(H2O)n(SiO(OH)3)]+ and no four-coordinated ligand substitution reaction is found. The most stable states in both systems show a distorted Ca[sbnd]O octahedral feature. Our findings may promote a fundamental understanding for the calcium silicate based species in solution and pre-nucleation process of C-S-H.
AB - Although the calcium silicate hydrate (C-S-H) has been used for millennium, the structure and formation of C-S-H are still unclear at atomistic level. In this work, we find two kinds of calcium silicate aqua complexes, [Ca(H2O)n(SiO2(OH)2)] and [Ca(H2O)n(SiO(OH)3)]+, prior to the nuleation of C-S-H. The ab initio metadynamics simulations show that [Ca(H2O)n(SiO2(OH)2)] and [Ca(H2O)n(SiO(OH)3)]+ have six and five stable states on the free energy surface (FES), respectively. There are different ligand substitution mechanisms between the FES minima. The four- and six- coordinated [Ca(H2O)n(SiO2(OH)2)] only follow associative and dissociative mechanisms, respectively. While both dissociative and associative mechanisms apply to the six-coordinated [Ca(H2O)n(SiO(OH)3)]+ and no four-coordinated ligand substitution reaction is found. The most stable states in both systems show a distorted Ca[sbnd]O octahedral feature. Our findings may promote a fundamental understanding for the calcium silicate based species in solution and pre-nucleation process of C-S-H.
KW - Ab initio metadynamics simulations
KW - Calcium silicate hydrate (C-S-H)
KW - Hydration
KW - Ligand substitution mechanisms
KW - Pre-nucleation
UR - https://www.webofscience.com/wos/woscc/full-record/WOS:000860772400002
UR - https://www.scopus.com/pages/publications/85126115816
U2 - 10.1016/j.cemconres.2022.106767
DO - 10.1016/j.cemconres.2022.106767
M3 - Journal Article
AN - SCOPUS:85126115816
SN - 0008-8846
VL - 156
JO - Cement and Concrete Research
JF - Cement and Concrete Research
M1 - 106767
ER -