Theoretical Prediction of CH<sub>n</sub> Crystal Structures under High Pressures
CH<sub>n</sub> is the precursor unit for graphene synthesis. We have theoretically predicated a series of CH<sub>n</sub> structures with n = 1, 2, 4, 6, 8, 10, and 12 at elevated pressures (ambient pressure, 50, 100, 200, 300, 350, and 400 GPa) using evolutionary algorithms....
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MDPI AG
2021-12-01
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| Series: | Crystals |
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| Online Access: | https://www.mdpi.com/2073-4352/11/12/1499 |
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| author | Tao Yang Jinjia Liu Xiaotong Liu Xiulei Liu Ning Li |
| author_facet | Tao Yang Jinjia Liu Xiaotong Liu Xiulei Liu Ning Li |
| author_sort | Tao Yang |
| collection | DOAJ |
| description | CH<sub>n</sub> is the precursor unit for graphene synthesis. We have theoretically predicated a series of CH<sub>n</sub> structures with n = 1, 2, 4, 6, 8, 10, and 12 at elevated pressures (ambient pressure, 50, 100, 200, 300, 350, and 400 GPa) using evolutionary algorithms. The predicted CH and CH<sub>2</sub> structures are graphane-type and polyethylene over the whole considered pressure range, respectively. The molecular crystalline methane is predicted for the stoichiometry of CH<sub>4</sub>. The combination of methane and H<sub>2</sub> for CH<sub>6</sub>, CH<sub>8</sub>, CH<sub>10</sub>, and CH<sub>12</sub> up to 300 GPa are obtained. At 400 GPa, the mixture of polymer and H<sub>2</sub> for CH<sub>6</sub>, CH<sub>10</sub>, and CH<sub>12</sub> comes into play. From the computed enthalpy, higher pressure and more hydrogen concentration contributed to the decomposition (to carbon and H<sub>2</sub>) of CH<sub>n</sub> systems. The total density of states for these CH<sub>n</sub> structures show that only the CH<sub>12</sub> phase is metallic above 300 GPa. The rotational properties are traced in H<sub>2</sub> and the CH<sub>n</sub> structures. The CH<sub>4</sub> rotation is more sensitive to the pressure. The H<sub>2</sub> units are nearly freely rotational. Other structures of CH<sub>n</sub>, including fcc-type and experimentally known structures, are not competitive with the structures predicted by evolutionary algorithms under high pressure region. Our results suggest that the CH<sub>n</sub> (n > 4) system is a potential candidate for hydrogen storage where H<sub>2</sub> could be released by controlling the pressure. |
| first_indexed | 2024-03-10T04:21:56Z |
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| institution | Directory Open Access Journal |
| issn | 2073-4352 |
| language | English |
| last_indexed | 2024-03-10T04:21:56Z |
| publishDate | 2021-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Crystals |
| spelling | doaj.art-6c3a30b07d4241da98689b729b6e23632023-11-23T07:48:33ZengMDPI AGCrystals2073-43522021-12-011112149910.3390/cryst11121499Theoretical Prediction of CH<sub>n</sub> Crystal Structures under High PressuresTao Yang0Jinjia Liu1Xiaotong Liu2Xiulei Liu3Ning Li4Beijing Advanced Innovation Center for Materials Genome Engineering, Computer School, Beijing Information Science and Technology University, Beijing 100192, ChinaBeijing Advanced Innovation Center for Materials Genome Engineering, Industry-University Cooperation Base between Beijing Information S&T University and Synfuels China Technology Co. Ltd., Beijing 101400, ChinaBeijing Advanced Innovation Center for Materials Genome Engineering, Computer School, Beijing Information Science and Technology University, Beijing 100192, ChinaBeijing Advanced Innovation Center for Materials Genome Engineering, Computer School, Beijing Information Science and Technology University, Beijing 100192, ChinaBeijing Advanced Innovation Center for Materials Genome Engineering, Computer School, Beijing Information Science and Technology University, Beijing 100192, ChinaCH<sub>n</sub> is the precursor unit for graphene synthesis. We have theoretically predicated a series of CH<sub>n</sub> structures with n = 1, 2, 4, 6, 8, 10, and 12 at elevated pressures (ambient pressure, 50, 100, 200, 300, 350, and 400 GPa) using evolutionary algorithms. The predicted CH and CH<sub>2</sub> structures are graphane-type and polyethylene over the whole considered pressure range, respectively. The molecular crystalline methane is predicted for the stoichiometry of CH<sub>4</sub>. The combination of methane and H<sub>2</sub> for CH<sub>6</sub>, CH<sub>8</sub>, CH<sub>10</sub>, and CH<sub>12</sub> up to 300 GPa are obtained. At 400 GPa, the mixture of polymer and H<sub>2</sub> for CH<sub>6</sub>, CH<sub>10</sub>, and CH<sub>12</sub> comes into play. From the computed enthalpy, higher pressure and more hydrogen concentration contributed to the decomposition (to carbon and H<sub>2</sub>) of CH<sub>n</sub> systems. The total density of states for these CH<sub>n</sub> structures show that only the CH<sub>12</sub> phase is metallic above 300 GPa. The rotational properties are traced in H<sub>2</sub> and the CH<sub>n</sub> structures. The CH<sub>4</sub> rotation is more sensitive to the pressure. The H<sub>2</sub> units are nearly freely rotational. Other structures of CH<sub>n</sub>, including fcc-type and experimentally known structures, are not competitive with the structures predicted by evolutionary algorithms under high pressure region. Our results suggest that the CH<sub>n</sub> (n > 4) system is a potential candidate for hydrogen storage where H<sub>2</sub> could be released by controlling the pressure.https://www.mdpi.com/2073-4352/11/12/1499CH<sub>n</sub> crystalevolutionary algorithmshigh pressure |
| spellingShingle | Tao Yang Jinjia Liu Xiaotong Liu Xiulei Liu Ning Li Theoretical Prediction of CH<sub>n</sub> Crystal Structures under High Pressures Crystals CH<sub>n</sub> crystal evolutionary algorithms high pressure |
| title | Theoretical Prediction of CH<sub>n</sub> Crystal Structures under High Pressures |
| title_full | Theoretical Prediction of CH<sub>n</sub> Crystal Structures under High Pressures |
| title_fullStr | Theoretical Prediction of CH<sub>n</sub> Crystal Structures under High Pressures |
| title_full_unstemmed | Theoretical Prediction of CH<sub>n</sub> Crystal Structures under High Pressures |
| title_short | Theoretical Prediction of CH<sub>n</sub> Crystal Structures under High Pressures |
| title_sort | theoretical prediction of ch sub n sub crystal structures under high pressures |
| topic | CH<sub>n</sub> crystal evolutionary algorithms high pressure |
| url | https://www.mdpi.com/2073-4352/11/12/1499 |
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