Hong-Ling Cui

First-principles study of the electronic and optical properties of a new metallic MoAlB

The structural, elastic, electronic and optical properties of MoAlB were investigated by first-principles calculations. The hardness of MoAlB is 12.71u2009GPa, which is relatively softer and easily machinable compared to the other borides. The analysis of the band structure and density (DOS) of states indicates that MoAlB has a metallic nature. The analysis of the electron localization function (ELF) shows that the Mo-B bond is a polar covalent bond with a short distance, which may increase the stability of the compound. The calculation of the phonon frequencies confirms the dynamical stability of MoAlB. Optical properties of MoAlB are investigated. In the energy range up to ~19u2009eV, MoAlB possesses high reflectivity and has the strongest absorption in the energy range of 0–23.0u2009eV. In addition, the plasma frequency of MoAlB is 20.4u2009eV and MoAlB can change from a metallic to a dielectric response if the incident light has a frequency greater than 20.4u2009eV.

C54Si6 heterofullerene as a potential gas sensor for CO, NO, and HCN detection

The adsorption of CO, NO, and HCN molecules on the C54Si6 heterofullerene is investigated on the basis of density functional theory calculations to exploit its potential applications as a gas sensor. The C54Si6 heterofullerene has two highly stable isomers (named isomer-1 and isomer-2). We find that the toxic CO, NO, and HCN molecules are chemically adsorbed on isomer-1 with moderate adsorption energies and apparent charge transfer. The electronic properties of isomer-1 are significantly influenced by the CO, NO, and HCN adsorption, especially its electric conductivity. The recovery time of the isomer-1 sensor for CO, NO, and HCN at room temperature is estimated to be short due to the medium (optimal) adsorption energies, indicating that isomer-1 (i.e. the most stable configuration) of C54Si6 heterofullerene should be a good CO, NO, and HCN sensor. Similar analysis indicates that the isomer-2 of C54Si6 heterofullerene is a potential efficient gas sensor for NO detection.

Adsorption of gas molecules on a graphitic GaN sheet and its implications for molecule sensors

Motivated by the recent realization of two-dimensional (2D) nanomaterials as gas sensors, we have investigated the adsorption of gas molecules (SO2, NO2, HCN, NH3, H2S, CO, NO, O2, H2, CO2, and H2O) on the graphitic GaN sheet (PL-GaN) using density functional theory calculations. It is found that among these gases, only SO2 and NH3 gas molecules are chemisorbed on the PL-GaN sheet with apparent charge transfer and reasonable adsorption energies. The electronic properties (especially the electric conductivity) of the PL-GaN sheet showed dramatic changes after the adsorption of NH3 and SO2 molecules. However, the strong adsorption of SO2 on the PL-GaN sheet makes desorption difficult, which precludes its application to SO2 sensors. Therefore, the PL-GaN sheet should be a highly sensitive and selective NH3 sensor with short recovery time. Furthermore, the adsorption of NO (or NO2) molecules introduces spin polarization in the PL-GaN sheet with a magnetic moment of about 1 μB, indicating that magnetic properties of the PL-GaN sheet are changed obviously. Based on the change of magnetic properties of the PL-GaN sheet before and after molecule adsorption, the PL-GaN sheet could be used as a highly selective magnetic gas sensor for NO and NO2 detection.

Exotic d0 magnetism in partial hydrogenated silicene

The intriguing d0 magnetic properties of partially hydrogenated silicene are investigated via first-principles calculations. H atoms are assembled along the diagonal line of 4u2009×u20094 supercell. The magnetism can be engineered through transforming the adsorption sites of H atoms. With odd number of H atoms, the systems demonstrate stable magnetism, and the total magnetic moment of each system is 1u2009μB. No magnetism is found in those systems with equal number of H atoms for sublattice A and sublattice B. Molecular dynamics simulations show the configurations and magnetism of the systems are stable at room temperature. Our work motivates promising applications for silicene in spintronics device.

Quantum-chemical studies of the structure and performance properties of 5-(1,2,4-triazol-C-yl)tetrazol-1-ols

Density functional theory was used to investigate IR spectra, heat of formation, and thermal stability of three energetic 5-(1,2,4-triazol-C-yl)tetrazol-1-ol compounds substituted at position 5 of the triazole ring. The detonation velocity and pressure were evaluated by using the Kamlet–Jacobs equations based on the packed density and solid-state heat of formation. The bond dissociation energies for the weakest bonds were analyzed to investigate the thermal stability of the title compounds. IR analysis shows that there are four main characteristic regions for the three compounds. Detonation velocity and pressure of the nitro derivative are higher than those of known explosive HMX, while the same characteristics of the nitroamino and azido derivatives are comparable to those of HMX. Bond dissociation calculations show that the N(5)–N(7) bond is the trigger bond during pyrolysis for all three compounds and the order of their thermal stability is azido > nitroamino > nitro. In addition, the energy gaps between the HOMO and LUMO of the studied compounds were also investigated and the obtained conclusion consistent with that of bond dissociation energy analysis.

Ab initio study of the structural, electronic, elastic and thermal conductivity properties of SrClF with pressure effects

Abstract SrClF is an important optical crystal and can be used as pressure gauge in diamond anvil cell at high pressure. In this work, we performed a systematic study on the structural, electronic and elastic properties of SrClF under pressure, as well as its thermal conductivity, by first-principles calculation. Different exchange-correlation functionals were tested and PBESOL was finally chosen to study these properties of SrClF. Studies reveal that SrClF has a bulk modulus of about 56.2 GPa (by fitting equation of states) or 54.3 GPa (derived from elastic constants), which agree well with the experimental result. SrClF is mechanically and dynamically stable up to 50 GPa. Its elastic constants increase with the applied pressure, but its mechanical anisotropy deteriorates as the pressure increases. Investigation of its electronic properties reveals that SrClF is a direct band-gap insulator with a gap value of 5.73 eV at 0 GPa, which decreases with the increasing pressure and the reason is found by analysing the partial density of states. Based on the calculated phonon dispersion curves, thermal conductivity of SrClF is predicated. At ambient conditions, the predicted thermal conductivity is about 3.74 Wm−1 K−1, while that obtained using the simplified Slack model give a slightly larger value of 4.62 Wm−1 K−1.

Theoretical investigation on vibrational spectra, first order hyperpolarizability and NBO analysis of 4-Phenylpyridinium hydrogen squarate

The vibrational frequencies of 4-Phenylpyridinium hydrogen squarate (4PHS) in the ground state have been investigated by using B3LYP/6-311++G(d,p) level. The analysis of molecular structure, natural bond orbitals and frontier molecular orbitals was also performed. The IR spectra were obtained and interpreted by means of potential energies distributions (PEDs) using MOLVIB program. NBO analysis proved the presence of C-H⋯O and N-H⋯O hydrogen bonding interactions, which is consistent with the analysis of molecular structure. The dipole moments and first-order hyperpolarizability (βtot) are calculated and are 5.856 D and 4.72×10(-30) esu, respectively. The high βtot value and the low HOMO-LUMO energy gap (4.062eV) are responsible for the optical and electron-transfer properties of 4PHS molecule. The photoresponse-related results indicate that 4PHS molecule is an excellent organic candidate of photon-responsive materials.

Density functional studies of small silicon clusters adsorbed on graphene

The structural and electronic properties of small Sin clusters (n = 1–6, 10) adsorbed on graphene are studied by use of density functional theory within periodic boundary conditions. Our results show that the structural properties of the deposited Sin clusters and graphene are weakly affected by their interaction. The adsorption energy difference of different adsorption sites for the same size Si cluster on graphene is very small, indicating the Sin-cluster–graphene system will be obtained easily. There is a little charge transfer from Sin clusters to graphene when the cluster size is larger. The adsorption of Sin clusters will be an effective method to open of an energy gap for graphene, which is useful for the applications of graphene to electrical and optical devices. Especially, the adsorption of Sin cluster with large size (n ≥ 5) would have a band gap with a constant energy value.

PCM Study of Bond Dissociation Energies of the S–NO Bond: A DFT Study

Quantum chemical calculations are used to estimate the equilibrium S–NO bond dissociation energies (BDEs) for seven S-nitro-N-acetyl-d,l-penicillamine dipeptides (SNAP-two peptides) in acetonitrile solution. These compounds were studied by employing the hybrid density functional theory (B3LYP, B3P86 and B3PW91) methods together with the 6-31G** basis set. The obtained results are compared with available experimental results. It is demonstrated that B3PW91 method is the best method to compute the bond dissociation energies of SNAP-two peptides. The substituent and solvent effects of the S–NO BDEs are further analyzed. The results show that S–NO BDE increases with the increment of isoelectric points of substituted groups. In addition, the S–NO BDE decreases due to the inclusion of solvent effects. Furthermore, SNAP-two peptides and the other NO-donors are compared.

Two-Dimensional Tetragonal GaN as Potential Molecule Sensors for NO and NO2 Detection: A First-Principle Study

Properties of gas molecules (NO, NH3, and NO2) adsorbed on two-dimensional GaN with a tetragonal structure (T-GaN) are studied using first-principles methods. Adsorption energy, adsorption distance, Hirshfeld charge, electronic properties, electric conductivity, and recovery time are calculated. It is found that these three molecules are all chemisorbed on the T-GaN with reasonable adsorption energies and apparent charge transfer. The electronic properties of the T-GaN present dramatic changes after the adsorption of NO2 and NO molecules, especially its electric conductivity, but NH3 molecule hardly changes the electronic properties of the T-GaN. Furthermore, the recovery time of the T-GaN sensor at T = 300 K is estimated to be quite short for NO2 and NO but very long for NH3. Moreover, the magnetic properties of the T-GaN are changed obviously due to the adsorption of NO (or NO2) molecule. Therefore, we suggest that the T-GaN can be a prominent candidate for application as NO2 and NO molecule sensors.