Daliang Sun

Study on the liquid inclusion induced light scatter in KDP crystal

In this paper we describe the formation of liquid inclusion induced light scatter in potassium dihydrogen phosphate crystal. The measurements were done by ultra-microscopy, TEM and AFM. The dimension of the scatter and the composition have been measured and a mechanism formation of the liquid inclusion induced scatter is proposed and discussed.

Cluster Formation in Solid–Liquid Interface Boundary Layers of KDP Studied by Raman Spectroscopy

The cluster formations in solid-liquid interface boundary layers of KDP crystals have been studied by Raman spectroscopy and ab initio cluster calculations with the density-functional theory. The calculations are made on H 2 PO 4 , H 4 P 2 O 8 , and H 4 P 4 O 16 clusters, which model the cluster structure in different growth layers. Excellent agreement has been achieved between vibrational frequencies predicted by theory and those observed in experiments. The present results also show that the desolvation process of polymer clusters takes place within the characteristic boundary layers. The growth unit of crystal growth is identified as H 4 P 2 O 8 dimer cluster.

Microprobe of structure of crystal/liquid interface boundary layers

The molecular structures and its evolutive regularities within the boundary layers in the crystal growth of KDP and DKDP have been studied in real time by using holography and Raman microprobe. The experiments show that the molecular structure of mother solution within the boundary layers is distinctly different from that of the solutions alone. In this paper, the effects of cations within the boundary layers on the structure of solution are considered. Within the characteristic boundary layers, the effects of cations cause the changes in O-P-O bond angle, electronic density redistribution of the phosphate groups, and significant changes in the bond intensity, thus leading to the breaking of partial hydrogen bonds of the phosphate associations, the readjustment of geometry of anionic phosphate groups and desolvation, and the forming of the smectic ordering structure of the anions-cations. Finally, the crystallization unit of anion-cation should be formed at the proximate interface.

Growth of cadmium mercury thiocyanate dimethylsulphoxide single crystal for laser frequency doubling

This paper reports the growth of an organometallic nonlinear optical (NLO) complex crystal, Cadmium mercury thiocyanate dimethyl-sulphoxide (CdHg(SCN)4(H6CP2OS)2, CMTD), which was grown from aqueous solution by a temperature lowering method. Its powder SHG intensity is higher than that of CMTC. The crystal size of CMTD can reach 25×23×15mm3. The solubility curve, and solubility variation with pH value are also reported. The growth habits of crystals of CMTD grown under different conditions are discussed and the optimized condition for the growth CMTD using a temperature-lowering method from aqueous solution are also discussed.

Vibrational Spectrum and Structure of CdHg(SCN)4 Single Crystals

The vibrational spectra of the cadmium mercury tetrathiocyanate (CMTC) single crystal have been studied by Raman spectroscopy and ab initio calculations with the Molecular Orbital (MO) theory using the GAUSSIAN 98 program. Agreement has been achieved between the vibrational frequencies predicted by the theory and those observed in Raman scattering experiments. The results show that the characteristic vibrational modes of the CMTC crystal arise mainly from the internal vibrations of the SCN, Cd(SCN) 4 , and Hg(SCN) 4 clusters. The three-dimensional network structure of the CMTC crystal is identified, and the high optical nonlinearity of the crystal is chiefly ascribed to the conjugated charge-transfer bridges (-Hg-S=C=N-Cd-) that connect all the distorted Cd(SCN) 4 and Hg(SCN) 4 tetrahedra together.

Growth kinetics on the (100) and (001) faces of TGS crystals

The growth kinetics and mechanisms on the (001) and (100) faces of TGS crystals were investigated. A phase contrast microscope with a CCD camera was used to observe the growth of the crystal. We found the growth on the (001) and (100) faces at high supersaturation was mainly controlled by a BCF surface diffusion mechanism. The kinetic data for the (100) face were also fitted by the nucleation and layer growth model of two-dimension nucleation at high supersaturation. Some important growth parameters for TGS crystals, such as edge energy, activation energy, and so on, were estimated.

Results of Biofeedback Therapy Together with Electrical Stimulation in Faecal Incontinence with Myogenic Lesions

Abstract Reports about biofeedback therapy together with electrical stimulation with faecal incontinence are rare. This study is to investigate the effectiveness of biofeedback therapy in faecal incontinence patients with myogenic lesions. Methods: One hundred and twenty-six patients with faecal incontinence caused by myogenic lesions were referred to this programme, comprising three sessions of supervised therapy in hospital followed by 2 months of home exercise. Biofeedback therapy methods that consist of strengthening muscles biofeedback, sensory discrimination biofeedback, synchronizing biofeedback, and electrical stimulation were selected to improve the programme. Clinical scores and outcomes of the anorectal function were assessed before and after the programme, and t test was performed for statistical analysis. Results : Before this programme, there were 19 patients with good clinical scores, 46 patients with fair and 61 patients with poor clinical scores. After therapy, 98 patients achieved good scores, 24 patients fair, and only four patients had poor clinical scores. The squeeze pressure and the sphincter electromyography amplitude were improved significantly, the rectal sensory threshold was decreased significantly, and 80 patients who previously had no external anal sphincter reflex acquired such a reflex. At the two-year follow-up, 60.2% (65/108) of patients maintained the clinical outcomes. Conclusion : biofeedback therapy together with electrical stimulation is an effective method for faecal incontinence in patients with myogenic lesions. Patients should be offered this choice of therapy.

Dual Elementary-Steps Growth Mechanism of CdHg(SCN)4(H6C2OS)2 Crystals

A new dual elementary-steps growth mechanism was observed during our research on the CdHg(SCN)4(H6C2OS)2 (CMTD) crystals. Namely two types of elementary-step sources with different step height can be produced on the same crystal surface during the growth of some crystals. Furthermore the sum of these elementary-step heights is equal to the corresponding interplanar distance dhkl. The heights of these elementary steps were determined by crystal structure as well as growth motif and they have no relation to crystal defects. The elementary steps referred in this paper are completely different to sub-step mentioned by Min in 1988. Only one step height h was included in normal growth rate formulas for the dominant crystal growth theories at present such as BCF spiral growth mechanisms and the classic two-dimensional nuclear growth modes. Without considering the effects of the dual elementary-steps h1 and h2 to the growth procedure, the classic formulas containing the parameter h (step height) should be modified when they are applied to the research on crystals growing with dual elementary-steps growth mechanism.