Computational studies of polyelectrolytes containing zeolitic fragments
- Northwestern Univ., Evanston, IL (United States)
- Argonne National Lab., IL (United States). Materials Science Div.
The structures and sodium affinities of a series of zeolitic fragments [H{sub 3}Al(OCH{sub 3}){sub x}(OSiH{sub 3}){sub 1{minus}x}{sup {minus}}, 2T, H{sub 2}Al(OCH{sub 3}){sub x}(OSiH{sub 3}){sub 2{minus}x}{sup {minus}}, Al(OCH{sub 3}){sub x}(OSiH{sub 3}){sub 4{minus}x}{sup {minus}}, 5T], that mimic the charge sites in polyelectrolytes are calculated by ab initio molecular orbital methods at different levels of theory. At the HF/6-31G{sup *} level, the decrease in the sodium affinity due to the substitution of an OCH{sub 3} group by an OSiH{sub 3} group is about 8 kcal/mol in the 2T and 3T systems. In the 5T systems, the replacement of a sodium-coordinated OCH{sub 3} group by an OSiH{sub 3} group causes a decrease of 7 kcal/mol in the sodium affinity, while the substitution for a non-sodium-coordinated OCH{sub 3} group results in a 2.7 kcal/mol decrease. The lower sodium affinity indicates a weaker Coulombic interaction, suggesting an enhanced ionic conductivity with the substitution of carbon by silicon, consistent with experimental results. Natural bond orbital (NBO) analyses show that silicon-bonded oxygen atoms have smaller lone-pair dipole moments, resulting in a lower sodium affinity. The substitution of aluminum by boron leads to a higher sodium affinity, although the effect of replacing an OCH{sub 3} group by an OSiH{sub 3} group still reduces the sodium affinity. The effect of the sodium cation on the bond angles in these systems is also investigated.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 682065
- Journal Information:
- Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical, Vol. 103, Issue 31; Other Information: PBD: 5 Aug 1999
- Country of Publication:
- United States
- Language:
- English
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