Role of Mg Impurity in the Water Adsorption over Low-Index Surfaces of Calcium Silicates: A DFT-D Study
Calcium silicates are the most predominant phases in ordinary Portland cement, inside which magnesium is one of the momentous impurities. In this work, using the first-principles density functional theory (DFT), the impurity formation energy (<i>E</i><sub>for</sub>) of Mg sub...
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MDPI AG
2020-07-01
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| Online Access: | https://www.mdpi.com/2075-163X/10/8/665 |
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| author | Chongchong Qi Qiusong Chen Andy Fourie |
| author_facet | Chongchong Qi Qiusong Chen Andy Fourie |
| author_sort | Chongchong Qi |
| collection | DOAJ |
| description | Calcium silicates are the most predominant phases in ordinary Portland cement, inside which magnesium is one of the momentous impurities. In this work, using the first-principles density functional theory (DFT), the impurity formation energy (<i>E</i><sub>for</sub>) of Mg substituting Ca was calculated. The adsorption energy (<i>E</i><sub>ad</sub>) and configuration of the single water molecule over Mg-doped β-dicalcium silicate (β-C<sub>2</sub>S) and M3-tricalcium silicate (M3-C<sub>3</sub>S) surfaces were investigated. The obtained Mg-doped results were compared with the pristine results to reveal the impact of Mg doping. The results show that the <i>E</i><sub>for</sub> was positive for all but one of the calcium silicates surfaces (ranged from −0.02 eV to 1.58 eV), indicating the Mg substituting for Ca was not energetically favorable. The <i>E</i><sub>ad</sub> of a water molecule on Mg-doped β-C<sub>2</sub>S surfaces ranged from –0.598 eV to −1.249 eV with the molecular adsorption being the energetically favorable form. In contrast, the <i>E</i><sub>ad</sub> on M3-C<sub>3</sub>S surfaces ranged from −0.699 eV to −4.008 eV and the more energetically favorable adsorption on M3-C<sub>3</sub>S surfaces was dissociative adsorption. The influence of Mg doping was important since it affected the reactivity of surface Ca/Mg sites, the <i>E</i><sub>ad</sub> of the single water adsorption, as well as the adsorption configuration compared with the water adsorption on pristine surfaces. |
| first_indexed | 2024-03-10T18:12:33Z |
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| language | English |
| last_indexed | 2024-03-10T18:12:33Z |
| publishDate | 2020-07-01 |
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| spelling | doaj.art-ecfce458de50494f919fa6e835795a792023-11-20T08:01:56ZengMDPI AGMinerals2075-163X2020-07-0110866510.3390/min10080665Role of Mg Impurity in the Water Adsorption over Low-Index Surfaces of Calcium Silicates: A DFT-D StudyChongchong Qi0Qiusong Chen1Andy Fourie2School of Resources and Safety Engineering, Central South University, Changsha 410083, ChinaSchool of Resources and Safety Engineering, Central South University, Changsha 410083, ChinaSchool of Civil, Environmental and Mining Engineering, University of Western Australia, Perth 6009, AustraliaCalcium silicates are the most predominant phases in ordinary Portland cement, inside which magnesium is one of the momentous impurities. In this work, using the first-principles density functional theory (DFT), the impurity formation energy (<i>E</i><sub>for</sub>) of Mg substituting Ca was calculated. The adsorption energy (<i>E</i><sub>ad</sub>) and configuration of the single water molecule over Mg-doped β-dicalcium silicate (β-C<sub>2</sub>S) and M3-tricalcium silicate (M3-C<sub>3</sub>S) surfaces were investigated. The obtained Mg-doped results were compared with the pristine results to reveal the impact of Mg doping. The results show that the <i>E</i><sub>for</sub> was positive for all but one of the calcium silicates surfaces (ranged from −0.02 eV to 1.58 eV), indicating the Mg substituting for Ca was not energetically favorable. The <i>E</i><sub>ad</sub> of a water molecule on Mg-doped β-C<sub>2</sub>S surfaces ranged from –0.598 eV to −1.249 eV with the molecular adsorption being the energetically favorable form. In contrast, the <i>E</i><sub>ad</sub> on M3-C<sub>3</sub>S surfaces ranged from −0.699 eV to −4.008 eV and the more energetically favorable adsorption on M3-C<sub>3</sub>S surfaces was dissociative adsorption. The influence of Mg doping was important since it affected the reactivity of surface Ca/Mg sites, the <i>E</i><sub>ad</sub> of the single water adsorption, as well as the adsorption configuration compared with the water adsorption on pristine surfaces.https://www.mdpi.com/2075-163X/10/8/665calcium silicatesfirst-principles DFTMg dopingwater adsorptionstructural and electronic properties |
| spellingShingle | Chongchong Qi Qiusong Chen Andy Fourie Role of Mg Impurity in the Water Adsorption over Low-Index Surfaces of Calcium Silicates: A DFT-D Study Minerals calcium silicates first-principles DFT Mg doping water adsorption structural and electronic properties |
| title | Role of Mg Impurity in the Water Adsorption over Low-Index Surfaces of Calcium Silicates: A DFT-D Study |
| title_full | Role of Mg Impurity in the Water Adsorption over Low-Index Surfaces of Calcium Silicates: A DFT-D Study |
| title_fullStr | Role of Mg Impurity in the Water Adsorption over Low-Index Surfaces of Calcium Silicates: A DFT-D Study |
| title_full_unstemmed | Role of Mg Impurity in the Water Adsorption over Low-Index Surfaces of Calcium Silicates: A DFT-D Study |
| title_short | Role of Mg Impurity in the Water Adsorption over Low-Index Surfaces of Calcium Silicates: A DFT-D Study |
| title_sort | role of mg impurity in the water adsorption over low index surfaces of calcium silicates a dft d study |
| topic | calcium silicates first-principles DFT Mg doping water adsorption structural and electronic properties |
| url | https://www.mdpi.com/2075-163X/10/8/665 |
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