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The hydrogen storage capacity of C(3)Ti and C(3)Ti(+) complex was studied using second order Møller-Plesset (MP2) and density functional theory (DFT) methods with different exchange and correlation functionals. Four and five H(2) molecules can be adsorbed on C(3)Ti and C(3)Ti(+) complex respectively at all the levels of theory used. This corresponds to the gravimetric H(2) uptake capacity of 8.77 and 10.73 wt % for the former and the latter respectively. The nature of interactions between different molecules in H(2) adsorbed complexes is also studied using many-body analysis approach. In the case of C(3)Ti(4H(2)) complex, total five-body interactions is negligible whereas for C(3)Ti(+)(5H(2)) relaxation energy is negligible. All the many-body energies have significant contribution to the binding energy of a respective complex. Atom-centered density matrix propagation molecular dynamics simulations were carried out using different methods to confirm whether H(2) molecules remain adsorbed on C(3)Ti and C(3)Ti(+) complex at room temperature. Adsorption Gibbs free energies show that four and five H(2) molecule adsorption on C(3)Ti and C(3)Ti(+) at room temperature is energetically favorable and unfavorable respectively using MP2 as well as DFT methods used here. H(2) adsorption is thermodynamically favorable over a wide range of temperature on the C(3)Ti than C(3)Ti(+)complex.

Density functional theory (DFT) and Fourth-order Möller-Plesset (MP4) perturbation theory calculations are performed to examine the possibility of hydrogen storage in V-capped VC(3)H(3) complex. Stability of bare and H(2) molecules adsorbed V-capped VC(3)H(3) complex is verified using DFT and MP4 method. Thermo-chemistry calculations are carried out to estimate the Gibbs free corrected averaged H(2) adsorption energy which reveals whether H(2) adsorption on V-capped VC(3)H(3) complex is energetically favorable, at different temperatures. We use different exchange and correlation functionals employed in DFT to see their effect on H(2) adsorption energy. Molecular dynamic (MD) simulations are performed to confirm whether this complex adsorbs H(2) molecules at a finite temperature. We elucidate the correlation between H(2) adsorption energy obtained from density functional calculations and retaining number of H(2) molecules on VC(3)H(3) complex during MDs simulations at various temperatures., (Copyright © 2011 Wiley Periodicals, Inc.)

We report the gravimetric hydrogen uptake capacity of C(2)H(4)Sc complex and isoelectronic ions using Density Functional Theory. We predict that C(2)H(4)Sc(+) can bind maximum seven hydrogen molecules in dihydrogen form giving gravimetric uptake capacity of 16.2 wt %, larger by about 2 and 4 wt % than the neutral and anion, respectively. We also found that the interaction of hydrogen molecules with C(2)H(4)Sc(+) ion is characteristically different than that with neutral and anion. Vibrational spectroscopic study reveals that C(2)H(4)Sc and isoelectronic ions are quantum mechanically stable with their characteristic change in respective identified mode. The large gravimetric H(2) uptake capacity of C(2)H(4)Sc(+) is well above the target specified by Department of Energy (DOE) by 2015., (Copyright 2010 Wiley Periodicals, Inc.)

Abstract: This work reports the interaction of molecular hydrogen with C2H2Ni, C2H4Ni complex and also with their dimer using density functional method. Maximum of two H2 molecules can interact with both C2H2Ni and C2H4Ni complex which corresponds to the gravimetric uptake capacity of 4.54 and 4.44 wt% respectively. No significant difference is observed either in structural parameters or in the adsorption energies after H2 adsorption on C2H2Ni and C2H4Ni complex. The calculated adsorption energies show that, the hydrogen molecules are strongly bound to both C2H2Ni and C2H4Ni complex. The Gibb’s corrected adsorption energies are positive for C2H2Ni(2H2) and C2H4Ni(2H2) complex even at higher temperature. Dimerization of C2H2Ni and C2H4Ni complex was carried out, which has reduced the gravimetric uptake capacity in case of C2H2Ni complex. A strong metal aggregation is observed during the dimerization process. The results from electronic structure method are confirmed using atom-centered density matrix propagation molecular dynamics simulations. [Copyright &y& Elsevier]

Density functional theory (DFT) and Fourth-order Möller-Plesset (MP4) perturbation theory calculations are performed to examine the possibility of hydrogen storage in V-capped VC3H3 complex. Stability of bare and H2 molecules adsorbed V-capped VC3H3 complex is verified using DFT and MP4 method. Thermo-chemistry calculations are carried out to estimate the Gibbs free corrected averaged H2 adsorption energy which reveals whether H2 adsorption on V-capped VC3H3 complex is energetically favorable, at different temperatures. We use different exchange and correlation functionals employed in DFT to see their effect on H2 adsorption energy. Molecular dynamic (MD) simulations are performed to confirm whether this complex adsorbs H2 molecules at a finite temperature. We elucidate the correlation between H2 adsorption energy obtained from density functional calculations and retaining number of H2 molecules on VC3H3 complex during MDs simulations at various temperatures. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011 [ABSTRACT FROM AUTHOR]

Using density functionals theory, we show that gravimetric hydrogen uptake of CHTi complex and its cation, CHTi, differ by about 2 wt%. Six and five hydrogen molecules are found to be adsorbed on CHTi and CHTi complexes thereby showing a hydrogen-uptake capacity of 13.74 and 11.72 wt%, respectively. All hydrogen molecules are adsorbed in molecular form on CHTi ion with an increase in metal bond strength, whereas in some cases, the hydrogen molecules are found to be dissociated on CHTi neutral complex. The uptake capacity of neutral CHTi complex shown in this work is in excellent agreement with that reported experimentally, Phillips and Shivaram (Phys Rev Lett 100:105505, ). The H adsorption energy and its dependence on exchange and correlation functions in density functionals method were illustrated. Even after the adsorption of maximum number of hydrogen molecules on CHTi and CHTi complexes, Ti and Ti remain strongly bound to CH substrate. [ABSTRACT FROM AUTHOR]

We report the gravimetric hydrogen uptake capacity of C2H4Sc complex and isoelectronic ions using Density Functional Theory. We predict that C2H4Sc+ can bind maximum seven hydrogen molecules in dihydrogen form giving gravimetric uptake capacity of 16.2 wt %, larger by about 2 and 4 wt % than the neutral and anion, respectively. We also found that the interaction of hydrogen molecules with C2H4Sc+ ion is characteristically different than that with neutral and anion. Vibrational spectroscopic study reveals that C2H4Sc and isoelectronic ions are quantum mechanically stable with their characteristic change in respective identified mode. The large gravimetric H2 uptake capacity of C2H4Sc+ is well above the target specified by Department of Energy (DOE) by 2015. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 [ABSTRACT FROM AUTHOR]