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We obtained the chemical shielding constants of 29 Si in Li 2 S–SiS 2 glass system on the basis of molecular orbital calculations. The relative chemical shieldings calculated at the HF/6-31G* level is −16.1 and −23.8 ppm for E (1) and E (0), respectively. These calculations are in good agreement with the previous NMR study: σ ( E (2))> σ ( E (1))> σ ( E (0)). It is found theoretically that incorporation of Li 2 S into SiS 2 does not influence the 29 Si chemical shift, while incorporation of Li 2 O into SiO 2 does to a significant extent. It is also found that the existence of oxygen in Li 2 S–SiS 2 glasses increases the chemical shielding of 29 Si by about 25 ppm, which is in good agreement with the experimental result.

The structure of organic–inorganic hybrid glass precursor Me2Si(OPO(OH)2)2 and low-melting glasses SnO–Me2SiO–P2O5 has been examined by 29Si static and MAS NMR, respectively. The 29Si MAS NMR spectra of SnO–Me2SiO–P2O5 were deconvoluted into three Gaussian peaks, whose chemical shifts were located at −3.1, −10.2 and −18.1 ppm. Ab initio molecular orbital calculations have also been carried out for the clusters modeling the structure of precursor and glasses. From the calculations of 29Si NMR shielding constants, the experimental chemical shifts at −10.2, −3.1 and −18.1 ppm were assigned to 29Si atoms in P–O–Si(Me)2–O–P network linkage, in P–O–Si(Me)2–OH terminating structure and in P–O–Si(Me)2–O–Si network linkage, respectively. Based on the area ratio of the assigned three peaks, the network structures around Si constructing SnO–Me2SiO–P2O5 low-melting glasses were discussed in detail.

Organic–inorganic hybrid precursors for new type low-melting glasses without pollution elements such as Pb and F have been synthesized through a non-aqueous acid–base reaction process. The hybrid compounds consist of –Si–O–P– framework, in which some of the bridging oxygens of a Si tetrahedron are substituted by organic functional groups. Terminating the oxide framework by the organic functional groups lowers the network dimension. Orthophosphoric acid (H 3 PO 4 ) and dialkyldichlorosilane (Me 2 SiCl 2 and Et 2 SiCl 2 ) were employed as starting materials. The formation of P–O–Si linkage was confirmed by IR spectra. The larger viscosity increase at higher Si concentrations is correlated to the formation of the linkage. It is proposed that an acid–base polycondensation reaction of P–OH+Si–Cl→P–O–Si+HCl↑ dominates the network formation. When dimethylsilane SiMe 2 is substituted by divalent Sn, an organic–inorganic hybrid low-melting glass in the system of SnO–Me 2 SiO–P 2 O 5 can be derived, the glass transition temperature of which is about 29 °C. So the present acid–base reactions provide a new process by which precursors for new type low-melting glass are synthesized.

Ab initio molecular orbital calculations at the Hartree–Fock/3-21G(*) level have been performed on several clusters modeling SiS2 glass. The clusters consist of edge-sharing and/or corner-sharing structural units that can be found in actual glassy SiS2. The experimental Raman spectrum of SiS2 glass was interpreted in terms of vibrational frequencies calculated for these model clusters. The observed Raman bands at 427 and 415 cm −1 were assigned to the breathing motions of S atoms localized in two (or more) and one edge-sharing units, respectively. We also propose that two peaks at 367 and 381 cm −1 occur as a result of an accidental degeneracy or a resonance between the vibrations of the corner- and edge-sharing S atoms. The corner-sharing structure which is isolated from or connected with one edge-sharing also contributes to these peaks around 370 cm −1 .

We provide a new method to predict the optical absorption of soda–lime-silicate glasses containing low levels (≲1 wt%) of iron. We assumed that octahedral and tetrahedral ferric iron as well as octahedral ferrous iron contribute to the optical absorption of the glasses. The absorption coefficients were determined for the respective colorants, and the total transmission spectra were calculated in the wavelength range from 200 to 2100 nm. It has been shown that the calculated spectra agree well with the experimental ones in the entire range of wavelength. We have further calculated such optical properties as visible light transmittance, total solar energy transmittance, and total solar ultraviolet transmittance. It has been demonstrated that these optical properties are satisfactorily reproduced by the calculations.

We have carried out ab initio molecular orbital calculations on clusters of atoms modeling the local structure of lithium and sodium metaphosphate glasses to investigate their structure and vibrational properties. The optimized structural parameters and O 1s photoelectron energies calculated at the Hartree–Fock/3-21G* level are in good agreement with the observed ones. We then performed frequency calculations for the lithium metaphosphate cluster. The calculated Raman spectrum agrees with the experimental one. On the basis of the calculated results, we interpret the vibrational spectra of alkali phosphate glasses and discuss the local coordination environments of alkali cations in the glassy system.

We propose a structural model of the blue-light-emitting center in silicon- and silica-based nanostructured materials on the basis of the dehydroxylation reaction of a pair of geminal silanol groups. This model predicts that the blue-light emission can be enhanced by introducing a large amount of surface silanol groups and the appropriate subsequent annealing. This enhancement of the PL emission is indeed observed in nanometer-sized amorphous silica particles with SiCl4.

Vibrational frequencies of TeO2 glass and their Raman scattering intensities have been computed at the Hartree-Fock level using small clusters modeling of the local structure of TeO2 glass. The calculations have successfully reproduced the observed Raman spectra of TeO2 glass. The calculated normal-mode coordinates have shown that the observed Raman bands at around 640 cm−1 are attributed to the vibrations localized within the TeO4 trigonal bipyramid, while the vibrations in the ranges 400–500 cm−1 and 720–780 cm−1 are due to the vibrations localized within the TeeqOaxTe linkage.

Ab initio molecular orbital calculations have been made for binary alkali metaphosphate glasses using H 2 P 2 O 7 R 2 (R = Li, Na, K, Rb) as molecular models. The calculations have demonstrated that lithium and sodium ions interact equally with two terminal oxygens in each PO 2 O − 2/2 tetrahedron, while potassium and rubidium ions interact favorably with one of the two terminal oxygens. The result indicates that the local environments of Na and Li are substantially different from those of K and Rb. The spectroscopic data observed for binary alkali metaphosphate glasses are also interpreted in terms of the molecular orbital concept.

Ab inition molecular orbital theory was applied to investigate the local structure of vitreous P2O5 and sodium phosphate glasses. Small clusters such as H4P2O7, H3P2O7Na and H2P2O7Na2 were employed to model the local structure of P2O5, Na2O · 2P2O5 and Na2O · P2O5 glasses, respectively, and their geometries were optimized at the 3-21G + d(O, P) level. Single-point calculations were then performed at the 3-21G + d(O, P, Na) level by using the 3-21G + d(O, P) geometries. The calculations have led to the following. First, each Na2O unit introduced into the phosphate network causes two POO32 tetrahedra to convert to two PO2O22− tetrahedra with only two different types of oxygen, namely, bridging and terminal oxygens. Second, The positive charge of Na+ is balanced by the negative charge which is almost equally delocalized between the two terminal oxygens in the PO2O22− tetrahedron. Finally, the average π-bonding character per PO bond decreases with increasing Na2O content. It has also been shown that the previous spectroscopic data for sodium phosphate glasses, such as X-ray photoionization, X-ray emission and UV excitation energies, and the composition dependence of the ionic conductivity for sodium phosphate and silicate glasses can be interpreted in terms of the present molecular orbital calculations.

A new mechanism of ionic transport for single- and mixed-alkali silicate glasses is presented on the basis of ab initio molecular orbital calculations on a clusters modeling of the local structure of alkali silicate glasses. The calculations clearly show that an alkali ion site is energetically matched with the occupying alkali ion; the distortion energies caused by the transfer of an alkali, A, to a vacant site previously occupied by an alkali, B, are calculated to be ≈ 67 to ≈ 670 kJ/mol. Owing to the large distortion energies, it is proposed that alkali ions in mixed-alkali glasses move through the glasses by an interchange with nearby silicons. This type of alkali transport is called the ‘interchange transport process’. It is characterized by random jumps and is most likely the origin of the mixed-alkali internal-friction peak. The mixed-alkali effect is well interpreted in terms of this type of alkali transport. That is, minor alkalis in mixed-alkali glasses do not migrate along the conduction pathways taken by major alkalis but make uncorrelated motions by the interchange transport process. Similarly, major alkalis migrate around minor alkalis by the interchange transport process. Further, it is shown that the interchange transport process plays an important role in the transport mechanism of modifier cations in low alkali (