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1Author    Takao OiRequires cookie*
 Title    Ab initio Molecular Orbital Calculations of Reduced Partition Function Ratios of Polyboric Acids and Polyborate Anions  
 Abstract    Molecular orbital calculations at the HF/6-3 lG(d) level were carried out for polyboric acids and poly-borate anions up to a pentamer to estimate their "B -to-B isotopic reduced partition function ratios (RPFRs) and examine the additivity of logarithms of RPFRs. Approximate RPFR-values calculated by the use of the additivity agreed with exact RPFR-values within a margin of 1% error. This error was equivalent to a 5% error on ln(RPFR). The equilibrium constants of mono boron isotope exhange reac-tions between three-coordinate boron and four-coordinate boron ranged from 1.0203 to 1.0360 at 25 °C, indicating the importance of exact evaluation of RPFRs of polymers. 
  Reference    Z. Naturforsch. 55a, 623—628 (2000); received March 18 2000 
  Published    2000 
  Keywords    Ab initio Molecular Orbital Calculations, Polyborates, Reduced Partition Function Ratios, Boron Isotope Exchange, Isotope Fractionation 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0623.pdf 
 Identifier    ZNA-2000-55a-0623 
 Volume    55 
2Author    Satoshi Yanase, Takao OiaRequires cookie*
 Title    A b initio Molecular Orbital Calculations of Reduced Partition Function Ratios of Hydrated Lithium Ions in Ion Exchange Systems  
 Abstract    Molecular orbital (MO) calculations at the HF/6-31G(d) level were carried out for the aquolithium ions, Li+(H20)" (n = 3, 4, 5, 6, 8, 10 and 12) and the aquolithium ions interacting with the methyl sul­ fonate ion (MeS-), Li+MeS~(H20)" (n = 0, 3,4, 5, 6, 7, 8 and 10) which were, respectively, intended to be substitutes for lithium species in the solution and resin phases of ion exchange systems for lithium isotope separation. For each of the species considered, at least one optimized structure with no negative frequency was obtained, and the 7Li-to-6Li isotopic reduced partition function ratio (RPFR) was esti­ mated for the optimized structure. The solvation number in the primary solvation sphere was four, both in the solution and resin phases; three waters and MeS" formed the primary solvation sphere in the res­ in phase. Additional water molecules moved off to the secondary solvation sphere. It was found that consideration on the primary solvation sphere alone was insufficient for estimations of reduced parti­ tion function ratios of aquolithium ions. Although the agreement between the experimentally obtained lithium isotope fractionation and the calculated results is not satisfactory, it is pointed out that the HF/6-31 G(d) level of the theory is usable for elucidation of lithium isotope effects in aqueous ion exchange systems. 
  Reference    Z. Naturforsch. 56a, 297—306 (2001); received February 15 2001 
  Published    2001 
  Keywords    Ab initio Molecular Orbital Calculations, Reduced Partition Function Ratios, Hydrated Lithium Ion, Lithium Isotope Effects, Ion Exchange 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0297.pdf 
 Identifier    ZNA-2001-56a-0297 
 Volume    56 
3Author    Takao Oi, Hidetake KakihanaRequires cookie*
 Title     
 Abstract    T h e o r e tic a l C o n s id e ra tio n on U r a n iu m Is o to p e E f fe c ts O b s e r v e d in C h e m ic a l U ra n iu m -2 3 5 E n r ic h m e n t P r o c e s s e s * This paper is dedicated to Professor J. Bigeleisen on the occasion oj his 70th birthday Theoretical consideration on the uranium isotope effects in chemical chromatographic uranium isotope enrichment processes are presented, making use of up-to-date spectroscopic, solution chem­ ical and separation factor data. It is shown that hydration of the uranyl (U02 +) and uranous (U4 +) ions has a profound effect on the reduced partition function ratios (RPFR's) of these ions and that, in accordance with experiment, the RPFR of the uranous ion is larger than that of the uranyl ion. Future prospects concerning the separation factors in chemical processes are mentioned. 
  Reference    Z. Naturforsch. 44a, 399—405 (1989); received December 30 1989 
  Published    1989 
  Keywords    Chemical processes for uranium isotope enrichment, Uranium isotope effects, Reduced partition function ratio, Separation factor, Uranyl and uranous ions 
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 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0399.pdf 
 Identifier    ZNA-1989-44a-0399 
 Volume    44