A theoretical study of the electronic and optical properties of the graphite intercalation compound K(NH3)(4)C-24
The electronic properties of the ternary potassium-ammonia graphite intercalation compound K(NH3)4C24 are studied using generalized gradient-corrected density functional theory, following recent theoretical and experimental studies on the microscopic structure and dynamics of intercalation compounds...
| Main Authors: | , |
|---|---|
| Format: | Journal article |
| Language: | English |
| Published: |
2002
|
| _version_ | 1797078887502446592 |
|---|---|
| author | Bernasconi, L Madden, P |
| author_facet | Bernasconi, L Madden, P |
| author_sort | Bernasconi, L |
| collection | OXFORD |
| description | The electronic properties of the ternary potassium-ammonia graphite intercalation compound K(NH3)4C24 are studied using generalized gradient-corrected density functional theory, following recent theoretical and experimental studies on the microscopic structure and dynamics of intercalation compounds of similar composition. Localized electronic states in the intercalant K-NH3 layer, whose existence has been postulated in order to explain peculiar features in the optical absorption of K(NH3)xC24 compounds with x ≃4 and, ultimately, the occurrence of a 2D metal-nonmetal transition at x ≃ 4.3, are shown to originate from the overlap of diffuse K-NH3 hybrid orbitals enveloping discrete K(NH3)4 clusters. This gives rise to a highly inhomogeneous conduction band extending in the inter-cluster region, which percolates throughout the crystal in narrow winding channels bounded by H atoms. The estimated frequency-dependent complex dielectric function is found to reproduce with remarkable accuracy the experimental spectra. In particular, we can establish a direct link between the intercalate state and the occurrence of the 1.85 eV peak in the ε2(ω) spectrum, a well-known feature specific to K-NH3 graphite intercalation compounds. Issues related to the actual occupation of the intercalate state (depending on the degree of charge back-transfer from the C sheets to the K-NH3 intercalate) are discussed within the limitations of a conventional electronic structure density functional approach. |
| first_indexed | 2024-03-07T00:37:58Z |
| format | Journal article |
| id | oxford-uuid:820f4605-5984-411c-813b-4c32f81e48ae |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T00:37:58Z |
| publishDate | 2002 |
| record_format | dspace |
| spelling | oxford-uuid:820f4605-5984-411c-813b-4c32f81e48ae2022-03-26T21:34:50ZA theoretical study of the electronic and optical properties of the graphite intercalation compound K(NH3)(4)C-24Journal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:820f4605-5984-411c-813b-4c32f81e48aeEnglishSymplectic Elements at Oxford2002Bernasconi, LMadden, PThe electronic properties of the ternary potassium-ammonia graphite intercalation compound K(NH3)4C24 are studied using generalized gradient-corrected density functional theory, following recent theoretical and experimental studies on the microscopic structure and dynamics of intercalation compounds of similar composition. Localized electronic states in the intercalant K-NH3 layer, whose existence has been postulated in order to explain peculiar features in the optical absorption of K(NH3)xC24 compounds with x ≃4 and, ultimately, the occurrence of a 2D metal-nonmetal transition at x ≃ 4.3, are shown to originate from the overlap of diffuse K-NH3 hybrid orbitals enveloping discrete K(NH3)4 clusters. This gives rise to a highly inhomogeneous conduction band extending in the inter-cluster region, which percolates throughout the crystal in narrow winding channels bounded by H atoms. The estimated frequency-dependent complex dielectric function is found to reproduce with remarkable accuracy the experimental spectra. In particular, we can establish a direct link between the intercalate state and the occurrence of the 1.85 eV peak in the ε2(ω) spectrum, a well-known feature specific to K-NH3 graphite intercalation compounds. Issues related to the actual occupation of the intercalate state (depending on the degree of charge back-transfer from the C sheets to the K-NH3 intercalate) are discussed within the limitations of a conventional electronic structure density functional approach. |
| spellingShingle | Bernasconi, L Madden, P A theoretical study of the electronic and optical properties of the graphite intercalation compound K(NH3)(4)C-24 |
| title | A theoretical study of the electronic and optical properties of the graphite intercalation compound K(NH3)(4)C-24 |
| title_full | A theoretical study of the electronic and optical properties of the graphite intercalation compound K(NH3)(4)C-24 |
| title_fullStr | A theoretical study of the electronic and optical properties of the graphite intercalation compound K(NH3)(4)C-24 |
| title_full_unstemmed | A theoretical study of the electronic and optical properties of the graphite intercalation compound K(NH3)(4)C-24 |
| title_short | A theoretical study of the electronic and optical properties of the graphite intercalation compound K(NH3)(4)C-24 |
| title_sort | theoretical study of the electronic and optical properties of the graphite intercalation compound k nh3 4 c 24 |
| work_keys_str_mv | AT bernasconil atheoreticalstudyoftheelectronicandopticalpropertiesofthegraphiteintercalationcompoundknh34c24 AT maddenp atheoreticalstudyoftheelectronicandopticalpropertiesofthegraphiteintercalationcompoundknh34c24 AT bernasconil theoreticalstudyoftheelectronicandopticalpropertiesofthegraphiteintercalationcompoundknh34c24 AT maddenp theoreticalstudyoftheelectronicandopticalpropertiesofthegraphiteintercalationcompoundknh34c24 |