Adsorption of NH3 and NO2 molecules on C48B6N6 heterofullerene: A DFT study on electronic properties

Adsorption of NH₃ and NO₂ molecules on the external surface of C₄₈B₆N₆ heterofullerene is investigated using DFT method. Attachment of NH₃ and NO₂ on C₄₈B₆N₆ heterofullerenes are compared with the bare C₄₈B₆N₆ model optimized at the B3LYP/6-31G^? level. The high surface binding energies indicates that ammonia undergoes chemical adsorption and could be compatible with the long recovery time but C₄₈B₆N₆ should be good NO₂ sensors with quick response as well as short recovery time. Total (TDOS) and partial (PDOS) density of state calculations is also considered to elucidate the difference in the NH₃ and NO₂ gas detection mechanism of C₄₈B₆N₆. The overlap population density of state (OPDOS) indicated that the chemical adsorption is due to the overlap of atomic orbitals below the Fermi level. The calculated results suggest that the C₄₈B₆N₆ heterofullerene is a suitable sensor material for NO₂ and is an ideal material for elimination and filtering of ammonia.     

Adsorption of water and ammonia on TiO2-anatase cluster models

Density functional theory (DFT) calculations performed at B3LYP/6-31G^∗∗ level are employed to study water and ammonia adsorption and dissociation on (1 0 1) and (0 0 1) TiO₂ anatase surfaces both represented by totally fixed and partially relaxed Ti₂O₉H₁₀ cluster models. PM3 semiempirical calculations were also conducted both on Ti₂O₉H₁₀ and Ti₉O₃₃H₃₀ clusters in order to assess the effect of cluster size. Following dissociation, the adsorption of H₂O and NH₃ by H-bonding on previously H₂O and NH₃ dissociated systems, respectively are also considered. It is found that the adsorption energies and geometries of water and ammonia molecules on (1 0 1) and (0 0 1) anatase cluster models depend on surface relaxation. The vibration frequency values are also calculated for the optimized geometries. The adsorption energies and vibration frequency values computed are compared with the available theoretical and experimental literature.     

Effect of tube radius on the exohedral chemical functionalization of boron-nitride zigzag nanotubes with NH3

The interaction between zigzag BNNTs with chirality index n=3–10 and ammonia has been studied at the level of B3LYP/6-31G^?. Ammonia can be chemically adsorbed on (3,0) to (7,0) BNNTs and physically adsorbed on other studied BNNTs. From NBO analysis charge transfer occur from NH₃ to BNNTs and change in the natural electron configuration of B atom of BNNTs at adsorption site for the (3,0) and (4,0) BNNTs cases is larger than others. The DOS result show that after functionalization of BNNTs with NH₃ molecules electronic properties of tubes are largely preserved and can be viewed as some kind of harmless modification. Electronic analysis revealed that the interaction of zigzag BNNTs with ammonia is more electrostatic (ionic) in nature, rather than the sole covalent and electrostatic nature increased with increasing of tube diameter.     

密度泛函理论研究硼掺杂富勒烯和锌卟吩间的准化学键相互作用 (cited: 1)

利用密度泛函(wB97XD/6-31G(d))对硼掺杂富勒烯C₅₉B和锌卟吩形成的超分子复合物C₅₉B-ZnP及其阴离子C₅₉B^{^-}-ZnP进行了研究. 结果表明硼掺杂富勒烯与锌卟吩间有强烈的相互作用,在C₅₉B-ZnP复合物中,富勒烯上的B原子与锌卟吩的N原子间形成准化学键相互作用. 与硼掺杂富勒烯的相互作用导致锌卟吩的电子吸收发生显著红移.     

Exohedral chemical functionalization of C48B6N6 with NH3: Binding energies and electronic structures of C48B6N6–(NH3)n=1−6

Theoretical study of exohedral chemical functionalization of C₄₈B₆N₆ with NH₃ molecules has been investigated using DFT. It was found that NH₃ molecule can be chemically adsorbed on boron sites of C₄₈B₆N₆, with a charge transfer from NH₃ to C₄₈B₆N₆. Adsorption energy and the quantity of electron charge transfer from latest adsorbed ammonia to C₄₈B₆N₆ decreased with increasing in the adsorbed NH₃ molecules. Despite the strong adsorption energies, electronic properties of C₄₈B₆N₆ is preserved after modification(s) with NH₃ molecule(s) and chemical modification of C₄₈B₆N₆ with NH₃ molecules can be viewed as some kind of safe modification.     

A first-principles study on the adsorption behaviour of methanol and ethanol over C59B heterofullerene

In the present study, the adsorption behaviour of methanol (CH₃OH) and ethanol (C₂H₅OH) molecules over heterofullerene C₅₉B surface is studied by density functional theory calculations. This heterofullerene is obtained from C₆₀ by substituting a carbon atom with a boron atom and relaxing self-consistently the structure to the local minimum. The adsorption of CH₃OH and C₂H₅OH on the C₅₉B is exothermic and the relaxed geometries are stable. The CH₃OH and C₂H₅OH adsorption can also induce a change in the highest occupied molecular orbital and the lowest unoccupied molecular orbital energy gap of the nanocage. The dehydrogenation pathways of CH₃OH and C₂H₅OH via O–H and C–H bonds scission are also examined. The results indicate that O–H bond scission is the most favourable pathway on the C₅₉B surface.     

Structural,magneto and optical properties of BX − 1NXC and BXNX − 1C cages (X = 12, 24 and 36)

The effect of carbon doping on the structural, optical and magneto properties of the B_XN_X cages has been studied using the B3LYP/6-31G^* level of density functional theory. With replacing one B or N atom with one C atom on the B_XN_X cages, the structural and symmetric properties, the optical absorption spectra and the band gaps of the B_XN_X cages change and the B_XN_X cages become magnetic. Our calculations conclude that the B_{X ? 1}N_XC and B_XN_{X ? 1}C cages can be interesting candidates for application in optoelectronics and spintronics.     

The effect of doping three Al and N atoms on the chemical shielding tensor parameters of the boron phosphide nanotubes: A DFT study

In this work, an armchair model of the (4,4) boron phosphide nanotubes (BPNTs) with a 1-nm length and consisting of 32 B and 32 P atoms is considered to study the influence of doping three atoms of aluminum in sites of boron (B_3AlPNTs) and three atoms of nitrogen in sites of phosphors (BP_3NNTs) on the electrostatic structure properties. The mouths of nanotubes are capped by hydrogen atoms in order to saturate the dangling bonds of the boundaries and to decrease the calculation time. The structures of BPNTs, B_3AlPNTs and BP_3NNTs are optimized by performing the level of density functional theory (DFT) using 6-31G^? basis set. The optimized structures are used for calculating the chemical shielding (CS) tensors and nuclear magnetic resonance parameters such as isotropic chemical shielding (CS^I) and anisotropic chemical shielding (CS^A). The results reveal that in both models of B_3AlPNTs and BP_3NNTs by doping N atoms the chemical shielding parameters of P and B atoms, which are directly connected to the Al and N atoms decreased and the other sites significantly changed.     

Magnetic resonance tensors in Uracil: Calculation of 13C, 15N, 17O NMR chemical shifts, 17O and 14N electric field gradients and measurement of 13C and 15N chemical shifts

The experimental ¹³C NMR chemical shift components of uracil in the solid state are reported for the first time (to our knowledge), as well as newer data for the ¹⁵N nuclei. These experimental values are supported by extensive calculated data of the ¹³C, ¹⁵N and ¹⁷O chemical shielding and ¹⁷O and ¹⁴N electric field gradient (EFG) tensors. In the crystal, uracil forms a number of strong and weak hydrogen bonds, and the effect of these on the ¹³C and ¹⁵N chemical shift tensors is studied. This powerful combination of the structural methods and theoretical calculations gives a very detailed view of the strong and weak hydrogen bond formation by this molecule. Good calculated results for the optimized cluster in most cases (except for the EFG values of the ¹⁴N3 and ¹⁷O4 nuclei) certify the accuracy of our optimized coordinates for the hydrogen nuclei. Our reported RMSD values for the calculated chemical shielding and EFG tensors are smaller than those reported previously. In the optimized cluster the 6-311+G** basis set is the optimal one in the chemical shielding and EFG calculations, except for the EFG calculations of the oxygen nuclei, in which the 6-31+G** basis set is the optimal one. The optimal method for the chemical shielding and EFG calculations of the oxygen and nitrogen nuclei is the PW91PW91 method, while for the chemical shielding calculations of the ¹³C nuclei the B3LYP method gives the best results.     

The influence of NH3 -attaching on the NMR parameters in the zigzag BN nanotube

Two models of (10, 0) boron nitride nanotubes (BNNTs), perfect and Ammonia-attached, were studied in order to evaluate the influence of NH₃-attaching on the B-11 and N-15 nuclear magnetic resonance in the (10, 0) boron-nitride nanotube (BNNT) for the first time. At first, based on density functional theory (DFT) each of the structures was optimized using B3LYP/6-31G (d) model chemistry. At the next step, the chemical-shielding (CS) tensors were calculated using the B3LYP/6-31G (d, p) level of theory in both of the relaxed forms and were converted to experimentally measurable nuclear magnetic resonance (NMR) parameters, i.e. chemical-shielding isotropic (CSI) and chemical-shielding anisotropic (CSA). Our calculation revealed that in the NH₃-attached BNNT (the most stable model) the B atom chemically bonded to the NH₃ molecule has the largest chemical-shielding isotropic (CSI) and the smallest chemical-shielding anisotropic (CSA) values among the other boron nuclei. Additionally, the NMR parameters of those nuclei directly bonded to the boron dramatically change while those of the other B nuclei remain almost unchanged.     

氮化钽团簇阴离子Ta3N3-解离吸附N2中的15N/14N同位素交换研究

氮气分子的吸附和活化是固氮研究中的重要过程. 近年来过渡金属氮化物由于在合成氨催化研究中的优异表现而受到广泛关注. 但是,氮化物物种与氮气分子在高温下反应的微观机制仍然不清楚,而该过程对于认识反应中的温度效应以及缩小气相团簇体系和凝聚相体系间的差距具有重要意义. 本文使用质谱观测到氮化钽团簇阴离子Ta₃¹⁴N₃^-和¹⁵N₂在高温下(393∽593 K)发生¹⁵N/¹⁴N同位素交换而产生¹⁴N₂/¹⁵N¹⁴N. 结合理论计算,阐述了同位素交换反应的微观机理以及升高温度对于N₂在Ta₃N₃^-上解离吸附的促进作用. 而在对比实验体系Ta₃¹⁴N₄^-/¹⁵N₂中,观察到升高温度只能加速¹⁵N₂在吸附产物Ta₃¹⁴N₄¹⁵N₂^-上的脱附. 这是由于氮空位是氮化物物种活化氮气的必要条件,而Ta₃N₄^-中由于不存在氮空位因此不能活化和解离氮气. 该研究为合成氨中氮化物物种中氮空位的作用提供了重要信息并且为固氮研究中高效催化剂的设计提供了线索.     

The structure and the analytical potential energy function of NH2 （X^2B1）

This paper reports that the equilibrium structure of NH2 has been optimized at the QCISD/6-311＋＋G （3df, 3pd） level. The ground-state NH2 has a bent （C2v, X^2B1） structure with an angle of 103.0582°. The geometrical structure is in good agreement with the other calculational and experimental results. The harmonic frequencies and the force constants have also been calculated. Based on the group theory and the principle of microscopic reversibility, the dissociation limits of NH2（C2v, X^2B1） have been derived. The potential energy surface of NH2（X^2B1） is reasonable. The contour lines are constructed, the structure and energy of NH2 reappear on the potential energy surface.     

NH3 adsorption on Ni(110) and the production of the NH2 species by electron irradiation

The adsorption of NH₃ on Ni(110) has been examined using electron stimulated desorption ion angular distribution (ESDIAD), low energy electron diffraction (LEED) and thermal desorption spectrometry (TDS). At ～ 85 K the NH₃ molecule enters into a series of chemisorption and physisorption states whose structures have been partially characterized by means of ESDIAD and LEED. Upon heating, these NH₃ states desorb without dissociation; for adsorption below 300 K there is essentially no thermal decomposition. The ammonia adiayer was found to be extremely sensitive to electron irradiation effects. Evidence was found to support the irradiation induced conversion of NH₃(ads) to an amido intermediate, nh_2(ads). The NH₂ adsorbs with its C_2v axis normal to the surface and its NH bonds aligned along the [001] and [001?] directions. In the absence of further electron irradiation the nh_2(ads) species is stable to 375 K whereupon it dissociates to N_(ads)and H_2(g). The remaining N_(ads) desorbs near 750 K with significant attractive N…N interaction. No evidence is found for an imido intermediate, nh_(ads). nh_2(ads) also undergoes a disproportionation/recombination reaction upon heating to produce an additional NH₃ desorption state. A significant isotope effect for NH versus ND scission, sensitive to the adsorption state of the ammonia, is found to occur upon electron irradiation.     

Ca掺杂的氧化铍纳米管吸附H2O和NH3的选择传感特

通过密度泛函计算, 借助NH₃和H₂O分子对未掺杂以及钙掺杂的BeO碳纳米管的结构和电传导性进行了研究. 结果发现,NH₃和H₂O分子可以吸附在纳米管侧壁的Be原子上,吸附能分别为约36.1和39.0 kcal/mol. 态密度分析显示BeO纳米管的电传导性在吸附后稍有变化. 对于NH₃和H₂O分子,纳米管表面的钙原子替换Be原子可使吸附能分别增加约7.4和14.7 kcal/mol. 与未掺杂纳米管不同的是,钙掺杂BeONT吸附NH₃和H₂O分子的电传导性更加敏感,且H₂O分子比NH₃分子更敏感.     

Electronic structure of solid C48N12 aza-fullerene

I report electronic structures and the cohesive energy for face-centered-cubic (fcc) solid C₄₈N₁₂ using generalized-gradient density-functional theory. The full vibrational spectrum of the C₄₈N₁₂ cluster is calculated within the harmonic approximation at the B3LYP/6-31G* level of theory. The results show that fcc is energetically preferred and a more stable crystal form than body-centered-cubic (bcc). C₄₈N₁₂ clusters are found to condense by a weak (0.29 eV) van der Waals force. The band gap of fcc C₄₈N₁₂ is calculated to be 1.3 eV at the GGA-PW91 level, whereas the HOMO-LUMO gap is calculated to be 2.74 eV using B3LYP/6-31G*.     

Theoretical study on C100 fullerenes and C96X4 (X=N,P, B,Si)

The geometrical structures and electronic properties of six fullerene isomers of C₁₀₀ were studied at the HF/6-31G^? and B3LYP/6-31G^? levels, respectively. The results of the fully optimized calculations show that three C₁₀₀ isomers 449:D₂, 425:C₁ and 442:C₂ are near isoenergetic isomers. The energies and properties of C₁₀₀ hexaanions were calculated. The C₁₀₀^6? (450:D₅) isomer is predicted to be the most stable isomer at the B3LYP/6-31G^? level, and the C₁₀₀^6? (449:D₂) isomer is 44.1 kcal/mol higher in energy. The heterofullerenes C₉₆X₄ (X=N, P, B, Si) formed from the initial C₁₀₀ (449:D₂) have also been investigated at the B3LYP/6-31G^? level. The HOMO–LUMO gaps and aromaticities show that the replacement of fullerene carbon atoms with four heteroatoms can enhance the electronic stabilization of C₁₀₀ (449:D₂).     

Th3Ni2B2N3 a possible new superconducting compound: insights from electronic band structure

La₃Ni₂B₂N₃, which is similar to YNi₂B₂C and related borocarbides, was earlier studied by the electronic structure calculations [D.J. Singh, W.E. Pickett, Phys. Rev. B 51 (1995) 8668.], and was predicted to be a 3-D metal. In search of new compounds of the borocarbide and related families to get higher T_C, we have studied the compound Th₃Ni₂B₂N₃, by the first principles full potential electronic structure calculations by the linear augmented plane wave method. We get similar band structure for Th₃Ni₂B₂N₃ as found for La₃Ni₂B₂N₃, and the various atom-split component density of states show similar properties. The total electron density of states at Fermi level has been increased to about 92 states per Ry per f.u. as compared to 57 states per Ry per f.u. in La₃Ni₂B₂N₃. The main increase is due to the increased hybridization of the 5f states as seen by the more prominent low energy tail in the Th-component density of states. Based on this enhancement we predict Th₃Ni₂B₂N₃ to be a high temperature superconductor with a T_c in excess of 30 K.     

The electronic and structural properties of BN and BP nano-cages interacting with OCN: A DFT study

The adsorption of OCN⁻ (cyanato anion) on boron nitride (B₁₂N₁₂ and B₁₆N₁₆) and boron phosphide nano-cages (B₁₂P₁₂ and B₁₆P₁₆) in terms of energetic, geometric, and electronic properties are studied using density functional theory calculations. Our study results indicated that the first OCN⁻ strongly prefers to be adsorbed from its N atom upon B atoms of the nano-cages than the O atoms of OCN⁻. These findings have been rationalized using frontier molecular orbitals and total electron density plots. The energy gap of the B₁₂P₁₂ is significantly reduced upon the adsorption of OCN⁻ compared to B₁₂N₁₂, thus leading to the increase in electrical conductance of nano-cage.     

Theoretical vibrational terms and rotational constants for the 15N substituted isotopologues of N2O calculated using normal hyperspherical coordinates

Variational calculations of the vibrational terms G_v and rotational constants B_v of the ¹⁴N¹⁵N¹⁶O, ¹⁵N¹⁴N¹⁶O and ¹⁵N¹⁵N¹⁶O isotopologues of nitrous oxide are carried out using normal hyperspherical coordinates. The Morse-cosine potential energy surface for N₂O previously determined by the authors by fitting to a set of experimental vibrational frequencies is employed. The G_v and B_v spectroscopic constants calculated for the ¹⁵N substituted isotopologues show an satisfactory agreement with those experimentally observed for a large number of vibrational bands of these isotopologues recently measured. Predicted calculated values of these spectroscopic constants for unobserved vibrational bands of the ¹⁵N substituted isotopologues are given in order to be of help in the identification and characterization of such bands, as a complement to the use of global effective Hamiltonians.     

Adsorption of oxygen molecular on pristine and defected SiC nanotubes

The structural and electronic properties of oxygen molecular adsorbed on the exterior surface of pristine and N_C or B_C defected (10,0) or (6,6) SiCNT have been investigated systematically using the first-principles projector-augmented wave potential within the density-functional theory under the generalized-gradient approximation. We find that for both pristine tubes the preferred adsorption sites of the O₂ molecule are above and nearly parallel to armchair Si-C bond whether physisorption or chemisorption. The strong chemical interaction between O₂ molecule and tube leads to not only a vanishing in magnetism of the O₂ molecule but also an outward relaxation of the underlying Si-C bond. The C atom substituted by N or B atom assists O₂ molecule adsorption above and nearly parallel to zigzag Si-N or Si-B bond as well as imparts a metallic character on the SiCNTs with higher concentration of the defects or a magnetism on the SiCNTs with lower concentration of the defects. Therefore, a combination of N or B doping followed by exposure to air may be an effective way to tune the electronic properties of the semiconducting SiCNTs. Furthermore, the lower binding energies for the pair of oxygen interstitials chemisorbed on N_C or B_C defected (10,0) or (6,6) SiCNT show that the oxygen molecule will dissociate to the pair of oxygen interstitials at the sidewall of N_C or B_C defected SiCNTs.