Lead iodide (PbI 2 ) is an important material for room temperature radiation detectors. In this paper, we have grown PbI 2 single crystal through a special craft, from which γ-ray detector has also been fabricated. X-ray diffraction analysis indicates structure of the grown crystal is 2H with hexagonal space group P3m1. Infrared transmission measurement shows transmission rate of the grown crystal sample (10×10×1mm 3 ) reaches 40% averagely in range of 400~4000cm . Ultraviolet absorbing test indicates cut-off wavelength of the sample is 547.6nm, corresponding band gap of 2.27eV. Room temperature detector fabricated from the grown crystal is sensitive to 241Am 59.5KeV γ-ray. Full width at half maximum (FWHM) of the obtained energy spectrum is 26.7KeV. All the results indicate the PbI 2 crystal grown through the special craft is of good characteristics and can be used for γ-ray detector.

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For liquid water in the far-infrared spectrum, phonons of molecular vibrations constitute two bands with a narrow gap at around 30 meV. Interestingly, there are two distinct peaks for ice in this gap. We demonstrated that the two peaks come from two kinds of translational modes. Considering different O–O–O bending constants, we yielded two frequencies based on the ideal model of ice Ic. These two kinds of vibrational modes do not exist in liquid water due to the collapse of the rigid tetrahedral structure. Thus, a window remains for ice resonance absorption with minimum energy loss in liquid water. A new method to decompose gas hydrates was proposed by supplying two terahertz radiation energies at ∼6.8 and 9.1 THz. This is also applicable to flow assurance in gas pipelines, aircraft deicers, and so on. Experimental measurements are expected to verify this finding along with the rapid development of a THz laser.

It is always a difficult task to assign the peaks recorded from a vibrational spectrum. Herein, we explored a new pathway of density functional theory (DFT) simulation to present three kinds of spectra of ice XIV that can be referenced as inelastic neutron scattering (INS), infrared (IR), and Raman experimental spectrum. The INS spectrum is proportional to the phonon density of states (PDOS) while the photon scattering signals reflect the normal vibration frequencies near the Brillouin zone (BZ) center. Based on good agreements with the experimental data, we identified the relative frequency and made scientific assignments through normal vibration modes analysis. The two hydrogen bond (H-bond) peaks among the ice phases from INS were discussed and the dynamic process of the H-bond vibrations was found to be classified into two basic modes. We deduced that two H-bond modes are a general rule among the ice family and more studies are ongoing to investigate this subject.

Despite its simple molecular structure, water is still a mystery to scientists. For the atomic and molecular vibrational modes of ice, as is well known, there are two kinds of vibrations: intra-molecular O—H stretching vibration and H—O—H bending vibration within the molecules and three kinds of molecular spatial rotations. However, thirty years ago, a high flux inelastic neutron scattering experiment showed that there are two distinct characteristic peaks in the far-infrared molecular translational vibration region of many ice phases. The origins of these peaks have not been determined till now. In this work, based on the CASTEP code, a first-principles density functional theory plane wave programme, the vibrational spectra as well as the vibrational normal modes of a series of ice phases are investigated. Two kinds of intrinsic hydrogen bond vibrational modes are first found in hydrogen-ordered ice Ic. Then it is found to be a general rule among ice family. Based on the ideal model, we prove that the two vibrational modes can be classified as four-bond vibration and two-bond vibration. There are many coupling modes in-between due to tetrahedral structure deformation under high pressure. Besides, there are also some optical vibrational modes with lower energy in the translational region, such as cluster vibrations and inter-plane vibrations. In Ice VII/VIII and XV/VI, each of which consists of two sublattices, there exist non-hydrogen bond vibrations. These molecular translational vibrations can explain all the far-infrared vibrational spectrum of ice phase, which makes up the last piece of the jigsaw puzzle for the molecular vibration theory of ice. The two vibrational modes do not exist in liquid water due to the collapse of the rigid tetrahedral structure. Thus, a window remains for ice resonance absorption with minimum energy loss in water. This theory is expected to be applicable to industrial deicing, food thawing, gas hydrate mining, and biomolecule frozen molding, etc.