Long-range intermolecular dispersion forces and circular dichroism spectra from first-principles calculations

This work presents first-principles calculations of long-range intermolecular dispersion energies between two atoms or molecules and of electronic circular dichroism spectra of chiral molecules. The former is expressed in terms of the C6 dipole-dipole dispersion coefficients Δε, and the latter is given in terms of the extinction coefficient. In a series of publications, the complex linear polarization propagator method has been shown to be a powerful tool to provide accurate ab initio and first-principles density functional theory results. This was the case not only for the C6 dispersion coefficients but also for the electronic circular dichroism at an arbitrary wavelength ranging from the optical to the X-ray regions of the spectrum. The selected samples for the investigation of dispersion interactions in the electronic ground state are the noble gases, n-alkanes, polyacenes, azabenzenes, alkali-metal clusters, and C60. It is found that the values of C6 for the sodium-cluster-to-fullerene interactions are well within the error bars of the experiment. The proposed method can also be used to determine dispersion energies for species in their respective excited electronic states. The C6 dispersion coefficients for the first π → π* excited state of the azabenzene molecules have been obtained with the adopted method in the multiconfiguration self-consistent field approximation. The dispersion energy of the π → π* excited state is smaller than that of the ground state. It is found that the characteristic frequencies ω1 defined in the London approximation of n-alkanes vary in a narrow range which makes it possible to construct a simple structure-to-property relationship based on the number of π-bonds for the dispersion interaction in these saturated compounds. However, this simple approach is not applicable to the interactions of the π-conjugated systems since, depending on the systems, their characteristic frequencies ω1 can vary greatly. In addition, an accomplishment of calculations of the electronic circular dichroism spectra in the near-edge X-ray absorption has been demonstrated

First-principles calculations of long-range intermolecular dispersion forces

This work presents first-principles calculations of long-range intermolecular dispersion energies between two atoms or molecules as expressed in terms of the C6 dipole-dipole dispersion coefficients. In a series of publications, it has been shown by us that the complex linear polarization propagator method provides accurate ab initio and first-principles density functional theory values of the C6 dispersion coefficients in comparison with those reported in the literature. The selected samples for the investigation of dispersion interactions in the electronic ground state are the noble gases, n-alkanes, polyacenes, azabenzenes, and C60. It has been shown that the proposed method can also be used to determine dispersion energies for species in their respective excited electronic states. The C6 dispersion coefficients for the first π → π* excited state of the azabenzene molecules have been obtained with the adopted method in the multiconfiguration self-consistent field approximation. The dispersion energy of the π → π* excited state is smaller r than that of the ground state. It is found that the characteristic frequencies ω1 defined in the London approximation of n-alkanes vary in a narrow range and that makes it possible to construct a simple structure-to-property relation based on the number of -bonds for the dispersion interaction in these saturated compounds. However, this simple approach is not applicable for the interactions of the π-conjugated systems since their characteristic frequencies ω1 vary strongly depending on the systems.Report code: LIU-TEK-LIC-2006:2</p

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dispersion coefficients for sodiu

Electric dipole polarizabilities and C6 dipole-dipole dispersion coefficients for alkali metal clusters and C60

The frequency dependent polarizabilities of closed-shell alkali metal clusters containing up to ten lithium, potassium, and rubidium atoms have been calculated using the linear complex polarization propagator approach in conjunction with Hartree – Fock and Kohn – Sham density functional theory. In combination with polarizabilities for C_{60} from a previous work [J. Chem. Phys. 123, 124312 (2005)], the C_6 dipole-dipole dispersion coefficients for the metal cluster-to-cluster and cluster-to-buckminster fullerene interactions are obtained via the Casimir – Polder relation. The B3PW91 results for the polarizabilities and dispersion interactions of the alkali metal dimers and tetramers are benchmarked against couple cluster calculations, and the whole series of calculations are compared against the corresponding work on sodium clusters [J. Chem. Phys. 125, 124306 (2006)]. The error bars of the reported theoretical results for the C_6 coefficients are estimated to be 8%.Original Publication:Auayporn Jiemchooroj, Bo. E. Sernelius and Patrick Norman, Electric dipole polarizabilities and C6 dipole-dipole dispersion coefficients for alkali metal clusters and C60, 2007, Journal of Computational Methods in Sciences and Engineering, (7), 5-6, 475-488.Copyright: IOS Presshttp://iospress.metapress.com

Electric dipole polarizabilities and C6 dipole-dipole dispersion coefficients for alkali metal clusters and C60

The frequency dependent polarizabilities of closed-shell alkali metal clusters containing up to ten lithium, potassium, and rubidium atoms have been calculated using the linear complex polarization propagator approach in conjunction with Hartree – Fock and Kohn – Sham density functional theory. In combination with polarizabilities for C_{60} from a previous work [J. Chem. Phys. 123, 124312 (2005)], the C_6 dipole-dipole dispersion coefficients for the metal cluster-to-cluster and cluster-to-buckminster fullerene interactions are obtained via the Casimir – Polder relation. The B3PW91 results for the polarizabilities and dispersion interactions of the alkali metal dimers and tetramers are benchmarked against couple cluster calculations, and the whole series of calculations are compared against the corresponding work on sodium clusters [J. Chem. Phys. 125, 124306 (2006)]. The error bars of the reported theoretical results for the C_6 coefficients are estimated to be 8%.Original Publication:Auayporn Jiemchooroj, Bo. E. Sernelius and Patrick Norman, Electric dipole polarizabilities and C6 dipole-dipole dispersion coefficients for alkali metal clusters and C60, 2007, Journal of Computational Methods in Sciences and Engineering, (7), 5-6, 475-488.Copyright: IOS Presshttp://iospress.metapress.com

C6 dipole-dipole dispersion coefficients for the n-alkanes: Test of an additivity procedure

We report on calculations of the dipole-dipole dispersion coefficients for pairs of n -alkane molecules. The results are based on first-principles calculations of the molecular polarizabilities with a purely imaginary frequency argument and which were reported by us in a previous work [P. Norman, A. Jiemchooroj, and Bo E. Sernelius, J. Chem. Phys. 118, 9167 (2003)]. The results for the static polarizabilities and dispersion coefficients are compared to simple algebraic expressions in terms of the number of CC and CH bonds in the two weakly interacting species. The bond additivity procedure is shown to perform well in the present case, and bond polarizabilities of 4.256 and 3.964  a.u . are proposed for the CH and the CC bond, respectively.Original Publication:Auayporn Jiemchooroj, Bo E. Sernelius and Patrick Norman, C6 dipole-dipole dispersion coefficients for the n-alkanes: Test of an additivity procedure, 2004, Physical Review A, (69), 44701, 44701.http://dx.doi.org/10.1103/PhysRevA.69.044701Copyright: American Physical Society http://www.aps.org

The presentation of self and formation of identity of adolescent girls in social media "Instagram" posts (2018 analysis)

Bakalaura darba “Pusaugu meiteņu sevis izrādīšana un identitātes veidošana sociālajā tīklā "Instagram" publicētajās fotogrāfijās (2018. gada analīze)” mērķis ir noskaidrot, kā pusaugu meitenes izrāda sevi, savu seksualitāti sociālā tīkla Instagram publicētajās fotogrāfijās. Darba teorētiskajā daļā aplūkota Ē. Gofmana identitātes izrādīšanas un veidošanas teorija, pusaudžu un sociālo mediju mijiedarbība, pusaugu meiteņu identitātes un seksualitātes veidošanās aspekti, kā arī attēla vizuālo analīze. Pētījumā veikta pusaudžu meiteņu Instagram publicēto fotogrāfiju kvantitatīvā kontentanalīze, elektroniska kvantitatīvā aptauja, kā arī daļēji strukturētā intervija ar Latvijas Universitātes profesori Dr.paed. Zandu Rubeni. Pētījuma rezultātā secināts, ka 81% no publicētā satura pusaudzes attēlo sevi nofotografētu no malas daļēji vai pilnā augumā vai uzņemot pašfoto. Seksualitāti pusaudžu meitenes 13-15 gadu vecumā vēl neakcentē atkailinot ķermeni, bet gan ieņemot dažādas pozas, kurā ķermeņa aprises redzamas caur drēbēm.The aim of bachelor thesis “The presentation of self and formation of identity of adolescent girls in social media "Instagram" posts (2018 analysis)” is to discover how adolescent girls present themselves and their sexuality in social media Instagram published photographs. The theoretical frame of the thesis includes the E.Goffman’s theory of self-presentation and identity constructing, the interaction between adolescents and social media, the formation of teenage girl’s identities and sexuality, as well as visual analysis of images. Research includes the quantitative content analysis of adolescent girl (13-15 years of age) Instagram posts, the quantitative online survey of teenage Instagram users and qualitative interview with professor Dr.paed. Zanda Rubene of University of Latvia. The study found out that 81% of the published content portrayed adolescent girls visible in full or partly height or selfies. Sexuality of teenage girls at the age of 13-15 is not displayed by posting revealing nude body parts, but through the use of different poses in which the body parts are visible through the clothes