Structures and electronic phases of the bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) clusters and κ-(BEDT-TTF) salts: A theoretical study based on ab initio molecular orbital methods J. Chem. Phys. 111, 5986 (1999); 10.1063/1.479894 Structures and the vibrational relaxations of size-selected benzonitrile-( H 2 O ) n=1-3 and -( CH 3 OH ) n=1-3 clusters studied by fluorescence detected Raman and infrared spectroscopies Ab initio geometry optimizations (HF/6-31G*) followed by single point energy calculations (MP2/6-31G*) suggest that the CH 4 ͑H 2 O͒ 20 cluster with a CH 4 molecule within the (H 2 O) 20 dodecahedral cavity has a stabilization energy ͑SE͒ of around 7 kcal/mol relative to separated CH 4 and (H 2 O) 20 molecules. The cavity of a 20 mer fused cubic or edge-shared prismic structure is too small to enclose a methane molecule. Even though the (H 2 O) 21 cluster with a water molecule within the dodecahedral cavity is significantly more stable ͑by around 28 kcal/mol͒ than CH 4 ͑H 2 O͒ 20 , the dodecahedral cage is too distorted in (H 2 O) 21 to form a fused hydrate structure. In CH 4 ͑H 2 O͒ 20 , on the other hand, the dodecahedral cage remains almost undistorted and hence, can form a fused hydrate structure. The present study also suggests that during a fused structure formation, each pentagonal ring sharing between two dodecahedral structures or a dodecahedral and a tetrakaidecahedral structures results in stabilization by around 20-23 kcal/mol.

The structures and stabilization energies (SE) of water clusters, (HzO),, with n = 8, 9, 12, 16, 20, and 21, were calculated by applying the intermediate neglect of differential overlap self-consistent field restricted Hartree-Fock method (INDO SCF RHF) after proper parametrization. These cluster structures include the neutral cubic forms for 8 and 9 mers, fused cubic 12, 16, 20, and 21 mers and cage structures for 16, 20, and 21 mers. In addition, the structure and SE values of the protonated fused cubic 20 and 21 mer clusters were calculated and compared with those of the cage structures. A closer examination of the fused cubic and the cage structures combined with the experimental evidence suggests that the fused structures are not likely to form. The present study also explains the observed magic numbers in experiments.

In the presence of KI, iodine crystals dissolve rapidly in an aqueous solution forming triiodide ions (I 3 -) and other neutral species. The experimental evidence does not support the formation of polyiodide ions such as I 5 -, I 7 -, etc. in the solution. However, there is a strong evidence suggesting the formation of polyiodine species, I 2x , where x ) 2, 3, etc., stabilized by H + ions in the solution. Ab initio results are presented for structures and energies of some of these species with an x value of up to 4. Each geometry optimization was done at the HF/LANL2DZ level followed by a single-point energy calculation at the MP2/LANL2DZ level. These calculations suggest that the isolated polyiodine species are not stable and, among the complexed species, the protonated clusters are most stable. IntroductionIt is a common observation that the solubility of iodine crystals in water is remarkably increased when KI is added to the solution. It is believed by many that the polyiodide ions such as I 3 -, I 5 -, I 7 -, etc., form in the aqueous solution 1-6 and take part in the formation of blue amylose iodine (AI) or more commonly known as starch-iodine complex. While a number of researchers considered the involvement of I 3 -ions with the complex, 1,2 others considered the involvement of I 5 -ions, 3-5 I 7 -ions, 6 or species without any I -ions. 6,7 Because of the lack of direct experimental results, the above controversy remained undiminished until very recently. Our recent experiment 8 with an iodide ion selective electrode (ISE) suggests that the iodide ions are not consumed in the AI complex forming reaction even when these ions are present in the solution. This finding suggests that the iodide ions are not required for the AI complex formation and, hence, one can ignore the possible involvement of I 3 -, I 5 -, and I 7 -species with the complex.To the best of our knowledge, the original consideration of these species, especially the larger ones, like I 5 -and I 7 -in the solution stemmed from the AI complex forming chemistry, and in view of the above ISE results it became necessary to reexamine the presence of polyiodide ions in the solution. It should be pointed out that the polyiodide ions such as I 3 -and I 5 -are known to exist 9-14 in solid crystal structures. However, their existence in aqueous solutions has never been confirmed. Even though the gas-phase theoretical studies predict significant stability for each of the I 3 -and I 5 -ions (relative to separated constituent molecules and ions), 15 it is not known whether they can survive frequent collisions with solvent molecules in the solution. In an aqueous solution, the following reactions can be considered for the formation of large polyiodide species,

The advanced molybdenum-based rare process experiment (AMoRE) aims to search for neutrinoless double beta decay ($$0\nu \beta \beta $$0νββ) of $$^{100}$$100Mo with $$\sim 100\,\hbox {kg}$$∼100kg of $$^{100}$$100Mo-enriched molybdenum embedded in cryogenic detectors with a dual heat and light readout. At the current, pilot stage of the AMoRE project we employ six calcium molybdate crystals with a total mass of 1.9 kg, produced from $$^{48}$$48Ca-depleted calcium and $$^{100}$$100Mo-enriched molybdenum ($$^{48{{\text {depl}}}}\hbox {Ca}^{100}\hbox {MoO}_{4}$$48deplCa100MoO4). The simultaneous detection of heat (phonon) and scintillation (photon) signals is realized with high resolution metallic magnetic calorimeter sensors that operate at milli-Kelvin temperatures. This stage of the project is carried out in the Yangyang underground laboratory at a depth of 700 m. We report first results from the AMoRE-Pilot $$0\nu \beta \beta $$0νββ search with a 111 kg day live exposure of $$^{48{{\text {depl}}}}\hbox {Ca}^{100}\hbox {MoO}_{4}$$48deplCa100MoO4 crystals. No evidence for $$0\nu \beta \beta $$0νββ decay of $$^{100}$$100Mo is found, and a upper limit is set for the half-life of $$0\nu \beta \beta $$0νββ of $$^{100}$$100Mo of $$T^{0\nu }_{1/2} > 9.5\times 10^{22}~\hbox {years}$$T1/20ν>9.5×1022years at 90% C.L. This limit corresponds to an effective Majorana neutrino mass limit in the range $$\langle m_{\beta \beta }\rangle \le (1.2-2.1)\,\hbox {eV}$$⟨mββ⟩≤(1.2-2.1)eV.

The expressions for density and fraction of H-bonding H atoms are derived and applied from supercooled to superheated states of liquid water (H2O). The anomalous density variation (around 4 °C) with temperature is explained solely on the basis of H-bonding and non-H-bonding (NHB) H atoms in the liquid. Interesting structural changes are postulated as the temperature of liquid water increases from a very low to a very high value. The limits of supercooling and superheating temperatures are calculated to be around 180 and 980 K, respectively, at 1 atm pressure.

The effects of calcium ion-chelating ligand (EDTA), heat, and enzyme concentration on the stability of a metalloenzyme (R-amylase, from Bacillus sources) solution have been examined by experimental as well as theoretical studies. A simple two-stage inactivation model has been presented that explicitly includes the calcium ion concentration and can explain all experimental results. The first stage involves a reversible inactivation process caused by the dissociation of a metal ion (Ca 2+ ) from the active enzyme molecule, followed by the second stage of inactivation in which the apoenzyme (protein without the metal) undergoes an irreversible thermal inactivation (denaturing). These studies also suggest that the diluted enzyme solution is more prone to inactivation than the concentrated enzyme solution.

UV−vis spectroscopic studies on aqueous solutions of iodine, potassium iodide, and α-cyclodextrin (αCD), (C6H10O5)6, suggest that a complex forms with the composition of αCD2I3 -. Semiempirical quantum mechanical PM3 calculations suggest that two major host−guest isomer types exist for this complex. The most stable isomer has the I3 - ion oriented almost parallel to the plane of one of the αCD molecules and sandwiched between two αCD molecules. The second sandwich isomer is less stable than the above isomer by about 5 kcal/mol (20.9 kJ/mol) and has the I3 - ion oriented vertically (along the vertical axis) between two αCD molecules. The formation constant (K f) of the complex is determined to be around 7.0 × 108 M-2 for both 15 and 25 °C.

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