• Title/Summary/Keyword: ab initio

Search Result 422, Processing Time 0.027 seconds

Covalent Organic Frameworks for Extremely High Reversible $CO_2$ and $H_2$ Uptake Capacity : A Multiscale Simulation Approach (우수한 가역적 이산화탄소 및 수소 저장성능을 가지는 공유결합성 유기적 골격구조체에 관한 다중스케일 접근법을 이용한 연구)

  • Choi, Yoon Jeong;Choi, Jung Hoon;Choi, Kyung Min;Kang, Jeung Ku
    • 한국신재생에너지학회:학술대회논문집
    • /
    • 2010.11a
    • /
    • pp.113.2-113.2
    • /
    • 2010

  • We report that the novel covalent organic frameworks (COFs) are capable of reversibly providing an extremely high uptake capacity of carbon dioxide and hydrogen at room temperature. These COFs are designed based on the multiscale simulations approach via the combination of ab initio calculations and force-field calculations. For this goal, we explore the adsorption sites of carbon dioxide and hydrogen on COFs, their porosity, as well as carbon dioxide adsorption isotherms. We identify the binding sites and energies of $CO_2$ on COFs using ab initio calculations and obtain the carbon dioxide adsorption isotherms using grand canonical ensemble Monte Carlo calculations. Moreover, the calculated adsorption isotherms are compared with the experimental values in order to build the reference model in describing the interactions between the $CO_2/H_2$ and the COFs and in predicting the $CO_2$ and $H_2$ adsorption isotherms of COFs. Finally, we design three new COFs, 2D COF-05, 3D COF-05 (ctn), and 3D COF-05 (bor), for the high capacity $CO_2/H_2$ and $H_2$ storage.

  • PDF

Conformations, Chemical Reactivities and Spectroscopic Characteristics of Some Di-substituted Ketenes: An ab initio Study

  • Gupta, V.P.;Sharma, Archna;Agrawal, S.G.
    • Bulletin of the Korean Chemical Society
    • /
    • v.27 no.9
    • /
    • pp.1297-1304
    • /
    • 2006

  • A systematic study of the structure, energetics and spectral characteristics of substituted aminoketenes $R(NH_2)$C=C=O (R = H, $CH_3$, $NH_2$, OH, $OCH_3$, CH=$CH_2$, C$\equiv$CH, CN, CHO, NO, $NO_2$) which are highly reactive and transient intermediates in synthesis has been conducted by ab initio calculations at the MP2/6- 31G*//MP2/6-31G* level. Twenty four stable isomers of the eleven substituted aminoketenes having dihedral angles $\phi NH_2\sim120{^{\circ}}$ and $60^{\circ}$ have been identified and their optimized geometries and energies obtained. Electrostatic and steric effects on the molecular geometries have been analyzed. While the $\pi$-acceptor groups lead to planar conformations, the electron-donor groups give rise to non-planar conformations. Isodesmic substituent stabilization energies relative to alkenes have been calculated and correlation with group electronegativities established. Role of induction effect by the substituent groups and resonance effects in charge distribution in the molecules has been analyzed. An analysis of the asymmetric stretching frequencies and intensities of the C=C=O group shows that affect of non-$\pi$ acceptor substituents on the frequency is determined by the field effect (F) and resonance effect (R) parameters, the calculated intensities I (km/mol.) are correlated to group electronegativities $x$ of the substituents by the relationship I = 640.2–100.1 $x$ (r = 0.92). The $\pi$-acceptor substituents increase the intensity which may be explained in terms of their delocalizing effect on the negative charge at the $C_{\beta}$ atom.

  • https://doi.org/10.5012/bkcs.2006.27.9.1297 인용 PDF KSCI