Theoretical predictions of two new chiral solid carbon oxides
Introduction
Since carbon dioxide effects on the climate change and the control of its global emission is a challenge today, carbon capture and utilization (CCU) becomes more and more attractive worldwide [1], [2], [3], [4], [5], [6], [7], [8]. Instead of substantial scale capital investment and geological storage, CCU provides us an alternative way to transfer them into some recyclable chemicals. Metal-organic frameworks (MOF) and some other metal-contaminated solids are considered to be used for the solidification process of carbon dioxide [9], [10], [11], [12]. However, this process requires a highly alkaline condition (pH > 11) and may make the secondary pollution of some common heavy metals in contaminated soils, such as Pb and Zn [13]. On the other hand, CO2 gas can be transferred to a polymerized solid phase directly under high pressure that avoids heavy metal pollution [14], [15]. Besides high pressure, other experimental and theoretical investigations of solid CO2 and the transition of different phases II-IV have also been reported [16]. Thus, the solid carbon oxide phase could have more potential applications for the CCU of CO and CO2.
Theoretical predictions and investigations of new solid carbon oxides can extend the field of CCU. In this paper, based on first-principles calculations, we proposed and investigated two new solid carbon oxides C6O9-154-6c6c3a and C6O9-154-6c6c3b, which have the oxygen/carbon ratio of 1.5 between the ratios of CO (1.0) and CO2 (2.0). Our calculations reveal that two carbon oxides not only are room-temperature stable but also could sustain their configurations at 1000 K. Additionally, both are indirect semiconductors with large band gaps, indicating that they may provide possible electronic resistance applications.
Section snippets
Computational methods
The traversal searching of new carbon oxide structures was performed by the genetic-algorithm method [17]. Several structures with the atoms' composition (C6O9) belonging to the space group P3221 were chosen as the first generations. After exploring one or more structures, the energy and the stability should be evaluated to confirm the stable configurations. The structural optimization and electronic properties were explored by the first-principle investigations based on density functional
Results and discussion
The crystal structures of two carbon oxides are schematically presented in Fig. 1. There are six carbon and nine oxygen atoms in the primitive cells. The carbon and oxygen ratio is 1:1.5 for each structure, which is between the ratios of CO (1:1.0) and CO2 (1:2.0). Both structures belong to space group P3221 (No. 154), which are both chiral ones. Two structures could be named as C6O9-154-6c6c3a and C6O9-154-6c6c3b, where C6O9 denotes the atoms' composition in the cell, 154 is the number of
Conclusion
Two carbon oxides (C6O9-154-6c6c3a and C6O9-154-6c6c3b) are theoretically predicted by first-principles calculations. Both structures belong to space group P3221, indicating that both are chiral structures. For each carbon oxide, there are six carbon atoms and nine oxygen atoms in the unit cell. Compared to their mass densities, C6O9-154-6c6c3b is denser than C6O9-154-6c6c3a. The energies data show that C6O9-154-6c6c3a is a little more energetically stable than C6O9-154-6c6c3b. Both phonon
CRediT authorship contribution statement
Sai Liu: Data curation, Formal analysis, Investigation, Writing - original draft. Yihua Lu: Data curation, Formal analysis, Investigation. Xi Zhu: Conceptualization, Funding acquisition, Investigation, Project administration, Supervision, Writing - review & editing. Min Wang: Conceptualization, Funding acquisition, Supervision, Validation, Writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work is supported by Shenzhen Fundamental Research Foundation (JCYJ20170818103918295), National Natural Science Foundation of China (Grant No. 21805234), President's funds from CUHK-Shenzhen (PF00728), Natural Science Foundation of Chongqing, China (Grant No. cstc2020jcyj-msxmX0009), and Chongqing Key Laboratory for Advanced Materials & Technologies of Clean Energies (Grant No. JJNY201902).
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