As a promising candidate for photoelectrochemical (PEC) water oxidation, the photoelectrochemical water splitting efficiency of hematite (Fe2O3) is limited by its low electron mobility. In this work, we report a new strategy for great enhancement of PEC water oxidation activity on Fe2O3. The S-doped Fe2O3 (S:Fe2O3) nanorods array on a Ti plate shows a substantially increased photocurrent density of 1.42 mA cm–2 at 1.23 V vs RHE in 1.0 M NaOH under simulated sunlight irradiation (AM 1.5G, 100 mW cm–2), 2.45 times that of Fe2O3 counterpart (0.58 mA cm–2). Both density functional theory calculations and experimental measurements verify that the superior activity is contributed to the enhanced electron mobility after S doping. This study offers an attractive photoanode in water-splitting devices for solar hydrogen production application.Keywords: Hematite; Photoelectrochemical water oxidation; S doping; Water-splitting devices;

A theoretical investigation on the structural stability, electronic, vibrational, and thermodynamic properties of the strontium apatites Sr10(PO4)6X2 (X = F, Cl, Br) is systematically conducted by the first-principles calculations. Results of cohesive energies and formation enthalpies suggest that the thermal stability of strontium apatites decreases from Sr10(PO4)6F2 (Sr-FAP) to Sr10(PO4)6Cl2 (Sr-ClAP) and further to Sr10(PO4)6Br2 (Sr-BrAP); such a tendency is also be observed with regard to the band gaps. Using linear-response approach, the detailed vibrational properties of Sr10(PO4)6X2 (X = F, Cl, Br) are obtained. According to the calculated phonon dispersions, it is concluded that strontium apatites Sr10(PO4)6X2 (X = F, Cl, Br) are dynamically stable, and the phonon behaviors are generally similar to these apatites, but most of the vibrational frequencies decrease from Sr-FAP, Sr-ClAP to Sr-BrAP. The assignment of the vibrational modes at the gamma point demonstrate that all the silent mode Bg, Bu and E2u are affected and the only optically active mode involved is the Raman active mode E2g with the replacement of larger Cl− and Br− for F−. The results calculated with the quasi-harmonic approximation (QHA) show that Sr10(PO4)6X2 (X = F, Cl, Br) exhibits similar but slightly different behaviors in terms of its thermodynamic properties, which is expected because the halogen atoms F, Cl and Br are in the same VIIA group. Significantly, all the present calculation results are satisfactory compared to the existing experimental and theoretical results.

There are two kinds of plutonium surface corrosion, one of which is oxidation between plutonium and oxygen or oxygen compounds. To investigate the corrosion mechanism of plutonium with oxygen, density functional theory (DFT) calculations have been carried out in the present study to investigate the interaction of plutonium atoms with oxygen molecules. Considering all possible spin states, a comprehensive description of the reaction mechanism is presented. All minima and transition state structures along the reaction pathway are optimized and the interaction energies and equilibrium distances were evaluated. The nature of the Pu–O bonding mode evolution along the reaction pathways was further validated using electron localization function (ELF) calculations, which indicated that the interaction could be considered as an electrostatic interaction in the entrance channel and a strong covalent interaction in the exit channel. We analyzed the density of states (DOS) for the minima and transition states, for the sake of analyzing the contribution of 5f electrons/orbitals in the title reaction. The results indicate that the most of the contributions to the HOMO come from the 5f orbitals of the plutonium atoms. Furthermore, reaction rate constants computed between 298 and 1000 K using variational transition state theory (VTST) suggest that Wigner tunneling effects are generally large for the reactions considered. Additionally, product energy distributions for the title reaction were evaluated by carrying out direct classical trajectory calculations. The results demonstrate that most of the available energy appears as the vibration energy of the products. The outcomes of the current theoretical studies provide detailed insights for understanding the interaction of plutonium with oxygen molecules.

Hydrogen molecules in a purge gas are known to enhance the release of tritium from lithium ceramic materials, which has been demonstrated in numerous in-pile experiments. The static computational results suggest that the molecular adsorption of H2 on the “ideal” Li2O/hydrogenated-Li2O (111) surface encounters high dissociation barriers in various entrance channels. The surface chemical inertness of the plane can be broken by introducing vacancy defects. In the present work, a combination of static DFT calculations and ab initio molecular dynamics has been performed to investigate the H2 dissociative mechanism. Our theoretical results, that the end-on oriented H2 could dissociate on the hydrogen monomer vacancy surface with one hydrogen atom ejected into the gas phase by the abstraction channel and the parallel H2 molecule dissociates on the hydrogen dimer vacancy surface with two hydroxyls forming, suggest that hydrogen vacancy defects facilitate the adsorption and dissociation of H2 molecule. The presence of the O2− ion induced by the hydrogen vacancy provides some low energy states in which the H2 electrons can be accommodated. This is very instructive for the comprehension of phenomena that occur during the operation of a thermonuclear reactor.

•The PBE0 hybrid density functional approach gives satisfying result for plutonium hydride comparing with experiments.•The ferromagnetic ground-state for PuH2+x is confirmed from theoretical perspective.•The complete phonon frequencies of PuH2+x at Γ point for the infrared and Raman modes are assigned.Plutonium (Pu) can react with hydrogen to form complicated continuous solid solutions with unusual chemical and physical properties. The PBE0 hybrid density functional under the framework of full-potential linearized augmented plane wave plus local orbitals is employed to investigate the structural, magnetic, lattice vibrations, and thermodynamic properties of face-centered cubic plutonium hydride (PuH2+x, x = 0, 0.25, 0.5, 0.75, 1). The decreasing trend with increasing x of the optimized lattice parameters is in reasonable agreement with experimental findings. According to the calculated formation enthalpies of PuH2+x compounds, all PuHx for both ferromagnetic(FM) and antiferromagnetic (AFM) phase are thermodynamically favorable, and the FM phase plutonium hydride is more favorable than the AFM phases. The characteristic Raman-active and the infrared-active modes at the center (Γ point) of the first Brillouin zone were further assigned and discussed. Finally, the free energy F, internal energy E, vibration enthalpy S, and constant-volume specific heat CV of PuH2+x are calculated in the range of 0–1000 K.

•More reasonable phonon mode assignments are got combining with experimental data.•The anomalous peak of specific heat is confirmed from theoretical perspective.•One reason of difficult to synthesize bulk single crystal is found from theory.The structural, lattice dynamics and thermodynamic properties of Sr2VO4 are systematically explored from ab initio density functional theory. In order to describe correlated phenomena among the localized V 3d electrons, DFT + U method have been used. The Born effective charges, and vibrational properties are calculated based on lattice dynamics theory. The calculated phonon wave numbers of infrared normal mode are found to be in consistency with experimental values available present. By comparing with the experimental data, we get more reasonable mode assignments. Additionally, some thermodynamic properties, e.g., Helmholtz free energy, entropy, and heat capacity, are also analyzed based on quasi-harmonic approximation. Comparison of the calculated specific heat at constant pressure P = 0 GPa with previous experimental data can further confirm the anomalous peak around 100 K due to the orbital ordering transition. The rapid increase of thermal expansion coefficient around the crystal growth temperature, 1000–1300 K, may be one reason of resulting in the difficulty of synthesizing the bulk single crystal phase.

•An effective interatomic pair potential for crystalline Li2SiO3 have been developed.•Simulated results using the constructed potential compare well with the DFT calculations and the experimental data.•The properties of mechanical and the thermodynamic, and Raman and Infrared active modes are calculated.We have developed an effective interatomic pair potential for crystalline Li2SiO3. The potential parameters are fitted by the optimized lattice parameters and calculated elastic constants. Based on constructed potential, the physical properties including mechanical properties, phonon dispersion curves, thermodynamic properties such as enthalpy, heat capacity and entropy are obtained by molecular statics (MS) simulation. The simulated results using the constructed potential compare well with the density functional theory (DFT) calculations and the experimental data. It indicates that the pair potentials we constructed in this paper are effective to model the structural, mechanical and thermodynamic properties of crystalline Li2SiO3.Download high-res image (482KB)Download full-size image

The knowledge of stoichiometries of alkaline-earth metal nitrides, where nitrogen can exist in polynitrogen forms, is of significant interest for understanding nitrogen bonding and its applications in energy storage. For calcium nitrides, there were three known crystalline forms, CaN2, Ca2N, and Ca3N2, at ambient conditions. In the present study, we demonstrated that there are more stable forms of calcium nitrides than what is already known to exist at ambient and high pressures. Using a global structure searching method, we theoretically explored the phase diagram of CaNx and discovered a series of new compounds in this family. In particular, we found a new CaN phase that is thermodynamically stable at ambient conditions, which may be synthesized using CaN2 and Ca2N. Four other stoichiometries, namely, Ca2N3, CaN3, CaN4, and CaN5, were shown to be stable under high pressure. The predicted CaNx compounds contain a rich variety of polynitrogen forms ranging from small molecules (N2, N4, N5, and N6) to extended chains (N∞). Because of the large energy difference between the single and triple nitrogen bonds, dissociation of the CaNx crystals with polynitrogens is expected to be highly exothermic, making them as potential high-energy-density materials.

We perform first principles calculations to investigate the structural, magnetic, electronic and optical properties of PuC and PuC0.75. Furthermore, we examine the influence of carbon non-stoichiometry on plutonium monocarbide. For the treatment of strongly correlated electrons, the hybrid density functionals like PBE0, Fock-0.25 are used and we compare the results with the generalized gradient approximation (GGA), local density approximation (LDA), LDA + U and experimental ones. The optimized lattice constant a0 = 4.961 Å for PuC in the Fock-0.25 scheme is the most close to the experimental data. The ground states of PuC and PuC0.75 are found to be anti-ferromagnetic. Our results indicate that additional removal of a C atom make lattice contract and new DOS peak appear in the near-Fermi region. We also compute and compare the optical properties of PuC and PuC0.75. The difference in optical properties between PuC and PuC0.75 should also be the influence of carbon vacancies.

We investigate the feasibility of laser cooling BBr and BCl using ab initio quantum chemistry. The multi-reference configuration interaction method (MRCI) is used to calculate the ground state X1Σ+ and the low-lying excited state A1Π, where Davidson modification with the Douglas–Kroll scalar relativistic correction is also taken into account. The calculated spectroscopic constants are in good agreement with available experimental values. The potential energy curves, permanent dipole moments (PDMs), transition dipole moments (TDMs) followed by Franck–Condon factors and radiative times for the transitions from the A1Π state to the ground state X1Σ+ are obtained as well. The determined Franck–Condon factors are highly diagonally distributed and the evaluated radiative lifetimes are of the order of nanoseconds. Furthermore, the a3Π → X1Σ+ transitions of BBr and BCl are also strongly diagonal and the X1Σ+ → A1Π transitions perhaps can be followed by the X1Σ+ → a3Π transitions to attain a lower Doppler temperature. Long-range behavior of BBr and BCl has also been studied, and a double well is found in the A1Π state of BBr. The shallow long-range well might open up even more channels for laser cooling of BBr. The results demonstrate the possibility of laser cooling BBr and BCl, and provide a promising theoretical reference for further research on BBr and BCl.

The feasibility of laser cooling BH and GaF is investigated using ab initio quantum chemistry. The ground state X 1Σ+ and first two excited states 3Π and 1Π of BH and GaF are calculated using the multireference configuration interaction (MRCI) level of theory. For GaF, the spin–orbit coupling effect is also taken into account in the electronic structure calculations at the MRCI level. Calculated spectroscopic constants for BH and GaF show good agreement with available theoretical and experimental results. The highly diagonal Franck–Condon factors (BH: f00 = 0.9992, f11 = 0.9908, f22 = 0.9235; GaF: f00 = 0.997, f11 = 0.989, f22 = 0.958) for the 1Π (v′ = 0–2) → X 1Σ+ (v = 0–2) transitions in BH and GaF are determined, which are found to be in good agreement with the theoretical and experimental data. Radiative lifetime calculations of the 1Π (v′ = 0–2) state (BH: 131, 151, and 187 ns; GaF: 2.26, 2.36, and 2.48 ns) are found to be short enough for rapid laser cooling. The proposed laser cooling schemes that drive the 1Π (v′ = 0) → X 1Σ+ (v = 0) transition use just one laser wavelength λ00 (BH: 436 nm, GaF: 209 nm). Though the cooling wavelength of GaF is deep in the UVC, a frequency quadrupled Ti:sapphire laser (189–235 nm) could be capable of generating useful quantities of light at this wavelength. The present results indicate that BH and GaF are two good choices of molecules for laser cooling.

•Our calculation indicates that γ-LiAlO2 is an insulator with a direct gap of 4.85 eV.•The complete phonon frequencies of γ-LiAlO2 at gamma point for the infrared and Raman modes are assigned.•The enthalpy H-H298 and entropy S of γ-LiAlO2 are in excellent agreement with the experiment values from 0 K to 1800 K.The structural, electronic, dynamical and thermodynamic properties of γ-LiAlO2 are investigated using density-functional perturbation theory (DFPT). The calculated structural parameters are found to differ by less than 0.5% from the available experimental data. The electronic band structure and DOS indicate that γ-LiAlO2 is an insulator with a direct gap of 4.85 eV. Using the linear response theory, vibrational properties are calculated. The phonon dispersion curves, the Born effective charges, the optical-mode frequencies at Г point and LO-TO splitting are reported for the first time. The Raman and infrared-active phonon modes are further assigned and discussed briefly. Our results indicate that the Born effective charges are −1.74 for O atom and +2.49 for Al atom, which are lower than the formal charges of Al and O atom, and the two giant LO-TO splitting occur in A2 and E modes. Additionally, the thermodynamic functions such as ΔF, ΔE, CV and S are predicted using the phonon density of states. The results are in good agreement with experimental values and other available theoretical results. It is expected that these results will provide useful guidance to help with structural characterization of LiAlO2.

•The ideal tensile strengths have been investigated.•The ideal shear strengths have been investigated.•Tensile and shear processes are associated with the transformation of electronic structure.•Cmcm uranium exhibits a high degree of mechanical anisotropy.The mechanical properties under large tensile and shear strains for orthorhombic uranium have been investigated systematically using the ab initio Density Functional Theory (DFT). We calculated the ideal tensile and shear strengths by incrementally deforming the simulation cell using first-principles total energy method. The obtained ideal tensile strengths are 21.3, 14.9, and 12.8 GPa in the [1 0 0], [0 1 0], and [0 0 1] crystalline directions, respectively, and the obtained ideal shear strengths are 14.3, 7.8, and 8.9 GPa in the (1 0 0)[0 1 1], (0 1 0)[1 0 1], and (0 0 1)[1 1 0] slip systems, respectively. In both cases, the present calculated results present typical mechanical anisotropy in different orthorhombic axes and slip systems. In particularly, the calculated electronic density of states (DOS) and the charge density of Cmcm uranium under the loading conditions consistently demonstrate that both tensile and shear deformation processes are intrinsically correlated with the evolution of electronic structure.Graphical abstractThe total and partial DOS as a function of tensile strains along the [0 0 1] direction.

The gas phase reaction of U atom with water molecule was investigated by means of the density functional theory calculations. Taking different possible spin states into account, a close description of the reaction mechanisms is presented. The nature of the chemical bonding evolution was investigated using diverse topological analyses including electron localization function and atoms in molecules.

•The PW91 functional calculated transition pressure of LaH2 is 10.38 GPa.•The mechanical stability of LaH2 under high pressure has been investigated.•The dynamical stability of LaH2 under high pressure has been studied.•LaH2 is stable up to 10.38 GPa, it may be metastable above 10.38 GPa up to 29 GPa.The pressure-induced disproportionation reaction phase transition, mechanical, and dynamical properties of LaH2 with fluorite structure under high pressure are investigated by performing first-principles calculations using the projector augmented wave (PAW) method. The phase transition of 2LaH2 → LaH + LaH3 obtained from the usual condition of equal enthalpies occurs at the pressure of 10.38 GPa for Perdew–Wang (PW91) functional and 6.05 GPa for Ceperly–Adler (CA) functional, respectively. The result shows that the PW91 functional calculations agree excellently with the experimental finding of 11 GPa of synchrotron radiation (SR) X-ray diffraction (XRD) of Machida et al. and 10 GPa of their PBE functional theoretical result. Three independent single-crystal elastic constants, polycrystalline bulk modulus, shear modulus, Young's modulus, elastic anisotropy, Poisson's ratio, the brittle/ductile characteristics and elastic wave velocities over different directions dependences on pressure are also successfully obtained. Especially, the phonon dispersion curves and corresponding phonon density of states of LaH2 under high pressure are determined systematically using a linear-response approach to density functional perturbation theory (DFPT). Our results demonstrate that LaH2 in fluorite phase can be stable energetically up to 10.38 GPa, stabilized mechanically up to 17.98 GPa, and stabilized dynamically up to 29 GPa, so it may remain a metastable phase above 10.38 GPa up to 29 GPa, these calculated results accord with the recent X-Ray diffraction experimental finding and theoretical predictions of Machida et al.

The gas phase reactions of U+ and U2+ with H2O were investigated using an ab initio molecular dynamics method. All of the information along the minimum energy path were calculated with density functional theory (DFT) and coupled cluster methods. For U+ with H2O, the molecular dynamics simulations yield a branching ratio of 86% for the H2 elimination channel to 14% for the H atomic elimination channel in agreement with the quadruple ion trap mass spectrometry (QIT/MS) experimental ratio of 91% to 9%. In the case of U2+ + H2O, there is a crossing of the potential energy surfaces (PES) after the first transition state. Crossing seams between the PES and possible spin inversion processes were studied by means of the intrinsic reaction coordinate (IRC) approach. For U2+ with H2O, all trajectories are corresponds to H atom elimination channel, this is consistent with the Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) experimental results. The chemical bonding evolution along the reaction pathways was discussed by using topological methodologies of the electron localization function (ELF).

Ce can be loaded with H forming complicated continuous solid solution and compounds, and causing remarkable electronic-structure changes. First-principles pseudopotential plane wave method with adding a Hubbard parameter U for considering the strong Coulomb correlation between localized 4f electron is employed to investigate the electronic and structural properties of stoichiometric and nonstoichiometric face-centered cubic (fcc) Ce hydrides (CeHx, x = 2, 2.25, 2.5, 2.75 and 3, respectively.). The most remarkable result is the decreasing trend of the calculated lattice parameters with increasing H composition, which is resulted from the associated effects of the enhanced chemical bonding owing to the participation of Ce 5d electron and, the size effects owing to the small H atomic radius and the large volume of octahedral interstice thus in favor of reducing the atomic distance for the formation of chemical bonding between Ce and octahedral H atoms.Highlights► Abnormal lattice contraction of Ce hydrides with increasing H is reproduced. ► Strong Coulomb correlation between localized 4f electron is reasonably considered. ► Contraction of lattice parameter results from the electronic and structural effects.

Ab initio calculations based on density functional theory have been carried to investigate the incorporation and solution of krypton in uranium dioxide. The GGA and GGA + U approximations were used with the projector-augmented-wave method. Several defects that are likely to accommodate the incorporation of krypton in UO2, such as oxygen and uranium vacancy, divacancy and Schottky defects were considered in this work. Both our SP-GGA and SP-GGA + U calculations suggested that the lowest incorporation energy corresponds to the divacancy. With SP-GGA method, the solution energies are positive whatever the trapping site considered, which confirms that Kr atoms are insoluble in UO2, but notable discrepancy exits between the results calculated by SP-GGA + U and SP-GGA. We highlight that the use of SP + GGA + U significantly increases the number of the energy minima of the system. Furthermore, the concentrations of the point defects and the solution energy of Kr for the different incorporation sites as a function of the stoichiometry were also obtained when the deviation from stoichiometry is small.Highlights► The incorporation and solubility of Kr in UO2 matrix were investigated in GGA and GGA + U methods. ► A 2 × 2 × 2 supercell were used with the fully relaxed cell parameters. ► With GGA calculations, Kr is insoluble in UO2. ► Notable discrepancy exits between the results calculated by SP-GGA and SP-GGA + U.

The crystal structures and electronic properties of hydrides LaNi4.5Al0.5H6−xHey(x=0,0.5,1.0)(x=0,0.5,1.0) have been investigated by means of the density functional theory using the full-potential linearized augmented plane wave (FLAPW) method with the generalized gradient approximation (GGA). The calculated data indicate that the micro-arrangement of hydrogen atoms in LaNi4.5Al0.5H6 is the same as that of hydride LaNi5H6, which is consistent with the experimental results in terms of the equilibrium desorption isotherms. And we found that once the first He atom locates in the tetrahedral interstitial sites (6m site) near Al atom for LaNi4.5Al0.5H5.5He0.5, then it is difficult for the second He atom to locate in the 6m site again. Therefore, the second He atom would prefer to occupy the middle plane site (6m\ast site) apart from Al atom for LaNi4.5Al0.5H5He. To study the interaction among La, Ni, Al, H and He atoms, the figures referring to the densities of states and contour maps of the electron densities on two different planes are analysed.

•Our calculation indicates that the α-LiAlO2 is an indirect band gap insulator of 6.319 eV.•The mechanical properties of α-LiAlO2 are predicted.•The complete phonon frequencies of α-LiAlO2 at gamma point for the infrared and Raman modes are assigned which to distinguish the α-LiAlO2 and γ-LiAlO2 in ITER and in MCFC.The physical properties including the structural, electronic, mechanical, lattice dynamical and thermodynamic properties of α-LiAlO2 are investigated using first-principles calculation. It is found that α-LiAlO2 is an insulator with an indirect gap of 6.319 eV according to band structure and density of states. The elastic constants are obtained and the results indicate that α-LiAlO2 is mechanically stable. The mechanical properties including bulk modulus (B), shear modulus (G), Young’s modulus (E), Poisson’s ratio (υ) are predicted with the value of 147.0 GPa, 105.2 GPa, 254.8 GPa and 0.211, respectively. The phonon dispersion curves and the phonon density of states are also calculated. The calculated phonon frequencies for the Raman-active and the infrared-active modes considering the LO-TO splitting are assigned. The two Raman active frequencies are 407.0 cm−1 of Eg mode and 628.8 cm−1 of A1g mode, and show satisfactory agreement with experiment. The thermodynamic functions such as ΔF, ΔE, CV and S is predicted by using the phonon density of states. These results provide valuable information for further insight into the properties of α-LiAlO2 in atomic scales, which is strategically important in ITER and in molten carbonate fuel cells (MCFC).

•The adsorption structures of H2O on Li2O (111) are obtained by calculations.•By Bader charge analysis, the charge translation from slab to adsorbate is found.•The vibrational frequencies of adsorbate are in line with the experimental values.The adsorption and dissociation mechanism of H2O molecule on the Li2O (111) surface have been systematically studied by using the density functional theory calculations. The parallel and vertical configurations of H2O at six different symmetry adsorption sites on the Li2O (111) surface are considered. In our calculations, it is suggested that H2O can dissociate on the perfect Li2O surface, of which the corresponding adsorption energy is 1.118 eV. And the adsorption energy decrease to be 0.241 eV when oxygen atom of H2O bonds to lithium atom of the slab. The final configurations are sensitive to the initial molecular orientation. By Bader charge analysis, the charge transfer from slab to adsorbed H2O/OH can be found due to the downward shift of lowest-unoccupied molecular orbital. We also analyze the vibrational frequencies at the Brillouin Zone centre for H2O molecule adsorbed on the stoichiometric surface. Due to the slightly different structure parameters, the calculated values of the vibrational frequencies of hydroxyl group range from 3824 to 3767 cm−1. Our results agree well with experimental results performed in FT-IR spectrum, which showed that an absorption peak of OH group appeared at 3677 cm−1 at room temperature.

The feasibility of laser cooling BH and GaF is investigated using ab initio quantum chemistry. The ground state X 1Σ+ and first two excited states 3Π and 1Π of BH and GaF are calculated using the multireference configuration interaction (MRCI) level of theory. For GaF, the spin–orbit coupling effect is also taken into account in the electronic structure calculations at the MRCI level. Calculated spectroscopic constants for BH and GaF show good agreement with available theoretical and experimental results. The highly diagonal Franck–Condon factors (BH: f00 = 0.9992, f11 = 0.9908, f22 = 0.9235; GaF: f00 = 0.997, f11 = 0.989, f22 = 0.958) for the 1Π (v′ = 0–2) → X 1Σ+ (v = 0–2) transitions in BH and GaF are determined, which are found to be in good agreement with the theoretical and experimental data. Radiative lifetime calculations of the 1Π (v′ = 0–2) state (BH: 131, 151, and 187 ns; GaF: 2.26, 2.36, and 2.48 ns) are found to be short enough for rapid laser cooling. The proposed laser cooling schemes that drive the 1Π (v′ = 0) → X 1Σ+ (v = 0) transition use just one laser wavelength λ00 (BH: 436 nm, GaF: 209 nm). Though the cooling wavelength of GaF is deep in the UVC, a frequency quadrupled Ti:sapphire laser (189–235 nm) could be capable of generating useful quantities of light at this wavelength. The present results indicate that BH and GaF are two good choices of molecules for laser cooling.

We investigate the feasibility of laser cooling BBr and BCl using ab initio quantum chemistry. The multi-reference configuration interaction method (MRCI) is used to calculate the ground state X1Σ+ and the low-lying excited state A1Π, where Davidson modification with the Douglas–Kroll scalar relativistic correction is also taken into account. The calculated spectroscopic constants are in good agreement with available experimental values. The potential energy curves, permanent dipole moments (PDMs), transition dipole moments (TDMs) followed by Franck–Condon factors and radiative times for the transitions from the A1Π state to the ground state X1Σ+ are obtained as well. The determined Franck–Condon factors are highly diagonally distributed and the evaluated radiative lifetimes are of the order of nanoseconds. Furthermore, the a3Π → X1Σ+ transitions of BBr and BCl are also strongly diagonal and the X1Σ+ → A1Π transitions perhaps can be followed by the X1Σ+ → a3Π transitions to attain a lower Doppler temperature. Long-range behavior of BBr and BCl has also been studied, and a double well is found in the A1Π state of BBr. The shallow long-range well might open up even more channels for laser cooling of BBr. The results demonstrate the possibility of laser cooling BBr and BCl, and provide a promising theoretical reference for further research on BBr and BCl.