It is a well recognized difficult task to simulate the vibrational dynamics of ices using the density functional theory (DFT), and there has thus been rather limited success in modelling the inelastic neutron scattering (INS) spectra for even the simplest structure of ice, ice Ih, particularly in the translational region below 400 cm⁻¹. The reason is partly due to the complex nature of hydrogen bonding (H-bond) among water-water molecules which require considerable improvement of the quantum mechanical simulation methods, and partly owing to the randomness of protons in ice structures which often requires simulation of large super-lattices. In this report, we present the first series of successful simulation results for ice Ih using DFT methods. On the basis of the recent advancement in the DFT programs, we have achieved for the first time theoretical outcomes that not only reproduce the rotational frequencies between 500 to 1200 cm⁻¹ for ice Ih, but also the two optic peaks at ∼240 and 320 cm⁻¹ in the translational region of the INS spectra [J. C. Li, J. Chem. Phys 105, 6733 (1996)]. Besides, we have also investigated the impact of pairwise configurations of H₂O molecules on the H-bond and found that different proton arrangements of pairwise H₂O in the ice Ih crystal lattice could not alter the nature of H-bond as significantly as suggested in an early paper [J. C. Li and D. K. Ross, Nature (London) 365, 327 (1993)], i.e., reproducing the two experimental optic peaks do not need to invoke the two H-bonds as proposed in the previous model which led to considerable debates. The results of this work suggest that the observed optic peaks may be attributed to the coupling between the two bands of H-O stretching modes in H₂O. The current computational work is expected to shed new light on the nature of the H-bonds in water, and in addition to offer a new approach towards probing the interaction between water and biomaterials for which H-bond is essential.

The vibrational spectrum of ice XI at thermal wavelengths using the CASTEP code, a first-principles simulation method, is investigated. A dual-track approach is constructed to verify the validity for the computational phonon spectrum: collate the simulated spectrum with inelastic neutron scattering experiments and assign the photon scattering peaks according to the calculated normal vibration frequencies. The 33 optical normal vibrations at the Brillouin center are illustrated definitely from the ab initio outcomes. The depolarizing field effect of the hydrogen bond vibrations at frequencies of 229 cm⁻¹ and 310 cm⁻¹ is found to agree well with the LST relationship. It is a convincing evidence to manifest the LO-TO splitting of hydrogen bonds in ice crystal. We attribute the two hydrogen bond peaks to the depolarization effect and apply this viewpoint to ordinary ice phase, ice Ih, which is difficult to analyse their vibration modes due to proton disorder.

Herein, via the first-principles density functional theory, CASTEP code, we investigated the 15 vibrational normal modes of ferroelectric hydrogen-ordered phase of ice Ic. The physical mechanism of hydrogen bond vibrations has been indicated by two type of peaks: the weak peak corresponds to two hydrogen bonds participating in the basal plane and the strong peak is composed by four hydrogen bonding vibrations for one molecule along the optic axis. The assignments of vibrational spectrum are individually conducted via the analysis of normal modes. The agreements of experimental data with the computed results manifest that the hydrogen-disordered bulk Ic may be composed by domains of a ferroelectric-ordered phase. We also predicted that the ferroelectric phase of ice Ic should show a birefringent phenomenon along the optical axis provided that a single crystal of the ferroelectric phase of ice Ic could be made.

In this work, pulse laser detectors based on the transverse thermoelectric effect of YBa₂Cu₃O_7-δ thin films on vicinal cut LaAlO₃ (001) substrates have been fabricated. The anisotropic Seebeck coefficients between ab-plane (S_ab) and c-axis (S_c) of thin films are utilized to generate the output voltage signal in such kind of detectors. Fast response has been determined in these sensors, including both the rise time and the decay time. Under the irradiation of pulse laser with the pulse duration of 5–7 ns, the output voltage of these detectors shows the rise time and the decay time of 6 and 42 ns, respectively, which are much smaller than those from other materials. The small rise time in YBa₂Cu₃O_7-δ-based detectors may be due to its low resistivity. While the high thermal conductivity and the large contribution of electronic thermal conductivity to the thermal conductivity of YBa₂Cu₃O_7-δ are thought to be responsible for the small decay time. In addition, these detectors show good response under the irradiation of pulse lasers with a repetition rate of 4 kHz, including the precise determinations of amplitude and time. These results may pave a simple and convenient approach to manufacture the pulse laser detectors with a fast response.

Based on first-principles density functional theory, we investigated the relationship between the vibrational normal modes and the spectrum of the newest laboratory-prepared ice phase, an empty clathrate hydrate structure from gas hydrate named ice XVII. A 48-molecule supercell was designed to mimic the hydrogen-disordered structure. Despite its much lower density than ice Ih, its phonon density of states shows features very similar to those of that phase. In our previous studies of ice Ic and ice XIV, we found two basic hydrogen bond vibrational modes in these hydrogen-ordered ice phases, which contribute two sharp hydrogen bond peaks in the translation region. In this study, we found that this rule also holds in the hydrogen-disordered phase ice XVII. A water molecule vibrating along its angle bisector possesses strong energy, because this vibrational mode involves oscillation against four bonded neighbors. In contrast, a water molecule vibrating perpendicular to its angle bisector has low energy because this mode involves only two of the molecule’s hydrogen bonds. This is an evidence in hydrogen-disordered ice and strengthens our proposal that the existence of two basic hydrogen bond vibrational modes is a general rule among ice family.