Xe-NH (X3∑-)体系的势能面和冷碰撞动力学研究

以超冷Xe原子感应冷却NH（X³∑^-）分子实验为背景,理论研究磁场中Xe和NH的冷碰撞动力学性质.通过从头算方法得到了解析表达的Xe-NH体系势能面,并在此基础上采用量子动力学计算方法,研究了磁场条件下NH低场追索态（n=0,m_j=1）的冷碰撞塞曼弛豫截面.结果表明超冷Xe原子感应冷却NH分子可能在实验上难以实施.     

700～85°C内H2O对CaO上NH3氧化的影响

本文验证了先前建立的FTIR定量方法对高H2O含量下NO和NH3测量的精度,研究了700～850°C内H2O对CaO上NH3氧化的影响.结果表明:含H2O高达15%时,NO和NH3的测量结果仍具有高精度,误差分别为±2%和±3%;H2O抑制CaO上NH3氧化的活性及副产物NO2的生成;NH3转化率随H2O浓度增大先迅速降低而后降低缓慢;同一温度下,NO产物选择性不随H2O浓度变化而改变;基于H2O Langmuir吸附于CaO表面竞争活性位,建立了H2O抑制CaO上NH3氧化的动力学模型,与实验结果符合良好.     

第一性原理研究Li_2NH的晶格动力学和热力学性质

采用第一性原理的赝势平面波方法系统地研究了Li_2NH的电子结构、晶格动力学和热力学性质.计算得到的晶格常数与先前的理论和实验结果符合得很好.运用线性响应理论计算了整个布里渊区高对称方向上的声子色散曲线和相应的声子态密度,发现Li_2NH(Pnma)声子色散曲线没有虚频,动力学性能相对最稳定,计算结果和先前实验及理论数据符合得很好.最后,利用得到的声子态密度进一步预测了Li_2NH的热力学性质,包括晶格振动对Helmholtz自由能、内能、熵和热容的贡献,计算结果在一定程度上可为Li-N-H储氢体系的应用提供理论指导.     

电子束脱硫副产物含硫量的测试分析

电子束烟气脱硫脱硝副产物成分十分复杂，主要为(NH4)2SO4和NH4NO3，还含有少量(NH4)2SO3、NH4NO2、(NH4)2S、NH4SO3NH2、有机胺、SiO2、铁锈和其他金属氧化物。若作为复合肥使用，应建立相应的测定手段对其各项指标进行测试，检验是否符合国家标准。本文用两种方法对脱硫副产物的含硫量进行了分析测试。     

C6H5COOH⋯X分子间氢键的理论研究

在B3LYP/6-311++G(3df,2p)理论水平,计算研究C6H5COOH...X分子间氢键的理论研究(X=H2O, HCOH, CH3COCH3, NH3, CH2NH和HCN)氢键体系。获得氢键复合物稳定结构、氢键相互作用能、振动频率、热力学性质等。计算结果表明,C6H5COO—H...X体系存在较强的O—H...O与O—H...N红移氢键。C6H5COO—H...X氢键复合物气态分子的自发形成过程温度不同,C6H5COOH...NH3和C6H5COOH...CH2NH 体系在室温下能自发进行,其余二聚体要在低温下才能自发进行。     

C6H5COOH⋯X分子间氢键的理论研究

在B3LYP/6-311++G(3df,2p)理论水平,计算研究C6H5COOH...X分子间氢键的理论研究(X=H2O, HCOH, CH3COCH3, NH3, CH2NH和HCN)氢键体系。获得氢键复合物稳定结构、氢键相互作用能、振动频率、热力学性质等。计算结果表明,C6H5COO—H...X体系存在较强的O—H...O与O—H...N红移氢键。C6H5COO—H...X氢键复合物气态分子的自发形成过程温度不同,C6H5COOH...NH3和C6H5COOH...CH2NH 体系在室温下能自发进行,其余二聚体要在低温下才能自发进行。     

用耦合簇理论及相关一致基研究NH2自由基的解析势能函数

运用CCSD(T)理论和Dunning等的系列相关一致基对NH2分子的基态结构进行了优化, 并使用优选出的cc-pV5Z基组对其进行了频率计算. 得到的结果是: 平衡核间距RNH= 0.10247 nm, 键角∠HNH = 102.947°, 离解能De = 4.2845 eV, 振动频率ν1(a1) = 1546.0342 cm-1, ν2(a1) = 3379.5543 cm-1和ν3(b2) = 3474.4784 cm-1. 对NH及H2分子, 使用优选出的cc-pV6Z基组对其基态的几何构型与谐振频率进行了计算并进行了单点能扫描, 且将扫描结果拟合成了解析的Murrell-Sorbie函数. 采用多体项展式理论导出了NH2分子的解析势能函数, 其等值势能图准确再现了NH2分子的离解能和结构特征. 报导了NH2分子对称伸缩振动等值势能图中存在的两个对称鞍点, 对应于反应NH+H→NH2, 势垒高度约为0.1378×4.184 kJ/mol.     

NH3与MgH2反应机理的密度泛函理论研究

采用密度泛函理论B3LYP方法研究了NH3与MgH2的放氢反应机理,在6-311G(d, p)基组水平上对反应物、中间体、过渡态及产物进行了全几何参数优化。频率分析和内禀反应坐标(IRC)计算证实了中间体和过渡态的正确性和相互连接关系。计算结果表明。反应分两步单通道的氢取代过程,且反应过程相类似,反应生成Mg(NH2)2和2H2。两步氢取代反应所释放的H2中两个H原子分别来源于NH3和MgH2。反应脱氢的关键在于克服N—H键断裂所需能量。     

3363/3364离子膜在NH_3-H_2O-LiBr吸收式制冷系统中的应用研究

由于NH3-H20-LiBr三元溶液中溴化锂的存在会使溶液性质发生改变,易于发生过程的进行,但阻碍了吸收氨的传质过程,对吸收性能不利.对此提出了一种膜分离技术,可将溴化锂从进入吸收器的溶液中分离出来,进而改善吸收性能.为检验对溴化锂的分离效果,采用装有3363/3364异相离子交换膜堆的膜分离装置进行实验。实验结果表明NH3-H20-LiBr三元溶液在膜分离器中一次循环后分离溴化锂的效率达90%,两次循环后分离效率达95%以上。基于上述实验中的分离效率,利用Aspen Plus模拟器,进一步模拟分析了带有这种膜分离装置的NH3-H20-LiBr三元吸收式制冷系统,并计算其性能系数.结果表明,与普通三元吸收式制冷系统相比,采用膜分离技术后,NH3-H20-LiBr吸收式制冷系统的性能系数可提高近10%.     

MOVPE生长GaN的表面反应机理

利用量子化学的 DFT 理论,对 MOVPE 生长 GaN 薄膜的表面初始反应机理进行研究。通过计算GaCH3和NH3在GaN(0001)-Ga面的4种吸附位的能量曲线发现,GaCH3在各吸附位的吸附能差值不大,因此容易在表面迁移;而NH3在各吸附位的吸附能差值较大,最稳定吸附位为Top位,迁移到其他位置需要克服较大能垒。在此基础上,提出了以NH3和 GaCH3为表面生长基元,在GaN(0001)-Ga面连续生长,最终形成环状核心的二维生长机理：在环状核心形成过程中,第1个GaN核生长需要3个NH3和1个GaCH3,可表示为Ga( NH2)3。第2个GaN核生长可利用已有的1个N作为配位原子,故只需2个NH3和1个GaCH3。2个GaN核可表示为( NH2)2 Ga-NH-Ga( NH2)2。第3个GaN核生长可利用已有的2个N作为配位原子,故只需要1个NH3和1个GaCH3。3个GaN核构成环状核心,可表示为Ga3( NH)3( NH2)3。后续的生长将重复第2个核和第3个核的生长过程,从而实现GaN薄膜的连续台阶生长。     

High-power,line-tunable14NH3 and15NH3 lasers

A high-power, line-tunable NH₃ laser pumped by a TEA CO₂ laser has been developed for application to laser isotope separation of tritium. Laser lines from¹⁵NH₃ are newly observed in a range from 11.24 to 13.23 m. The performance of an¹⁵NH₃ laser is compared to that of an¹⁴NH₃ laser.     

Absorption spectra of NH4MnCl3 and NH4MnF3

The absorption spectra of NH₄MnCl₃ and NH₄MnF₃ crystals have been measured down to 10 K in the 250 to 600 nm region. The observed bands are assigned to electronic transitions from the ⁶A_1g(S) ground state to various excited levels of Mn²⁺ ions in an octahedral crystalline field. The position of the bands have been fitted within the strong crystal field scheme. Resulting parameters at room temperature are B=741, C=2990 and Dq=520 cm⁻¹ for NH₄MnCl₃ and B=800, C=3139 and Dq=694 cm⁻¹ for NH₄MnF₃. At low temperature some bands show a rich fine structure in which some phonon progressions have been identified.     

A shock-tube study of NH3 and NH3/H2 oxidation using laser absorption of NH3 and H2O

Ammonia (NH₃) is an attractive carbon-free fuel, yet its low reactivity presents many challenges for direct use in combustion applications. These combustion challenges could be resolved by mixing NH₃ with more reactive fuels such as hydrogen (H₂). To further contribute to NH₃ and NH₃/H₂ kinetics—which arguably still requires much improvement—new experiments were conducted over a wide range of temperatures (1474–2307 K), near-atmospheric pressure, several NH₃/O₂ mixtures (equivalence ratios varying from 0.56 to 2.07), and near-stoichiometric NH₃/H₂/O₂ mixtures with NH₃:H₂ ratios of 80:20 and 50:50. During these experiments, laser absorption diagnostics near 10.4 µm and 7.4 µm were simultaneously employed to measure NH₃ and H₂O time histories, respectively. Characteristic parameters, such as NH₃ half-life time and H₂O induction delay time, were extracted from the time-history profiles, and these parameters present stringent speciation targets for mechanism validation. After an assessment of most modern kinetics models, three, most accurate, mechanisms were compared against the experimental results. Only one model was able to partially reproduce the pure NH₃ experiments, yet none of the models were capable of predicting the NH₃/H₂ experiments. Reaction pathway analysis showed that NH₃ oxidation proceeds via forming NH₂ then followed three different routes to form N₂. Importantly, the models considered showed different levels of importance for each route. Sensitivity analysis showed that the NH₃/H₂ experiment is mostly sensitive to NH₃+OH⇄NH₂+H₂O. Interestingly, this reaction showed no sensitivity for the NH₃/O₂ experiments. Overall, the models exhibited significantly slower reactivity than the NH₃/H₂ experiments, and the kinetics analysis showed that the start of this reactivity is governed by the levels of H-atoms in the early stages of the experiments. At these early stages of the experiments, propagation and branching reactions in the H₂/O₂ system are the main contributors to generating H radicals, along with the reaction NH₃+H⇄NH₂+H₂ which proceeds in its reverse direction.     

The ν4 state inversion spectra of 15NH3 and 14NH3

The frequencies and assignments of 45 inversion transitions of ¹⁵NH₃ and 15 additional inversion transitions of ¹⁴NH₃ in the ν₄ state are reported. The J = 0 inversion frequency and K-type doubling constant for K,l = 2, ?1 are 31 602.72 MHz and 2.000 MHz for ¹⁵NH₃. The expression containing the effective l-type doubling constant, q₀ - 5q_J - Δη…, is calculated from the (J,K,l) = (1,1,1), (1,1,?1), (2,1,1), and (2,1,?1) transitions as 10 166.022 MHz. The contribution to this expression from the Coriolis coupling with 2ν₂ is estimated for ¹⁴NH₃.     

Phase Transition in the Compound NH3(CH2)5NH3TlCl5

Penthylene diammonium pentachlorothallate(III) exhibits a phase transition at 316 K <artwork name="GPHT21157eu1"> This transition has been characterized by optical birefringence, dielectric measurements differential scanning calorimetry and spectroscopic measurements on polycrystalline samples. The space group and the cell parameters of phase I were determined by X-ray diffraction from single crystals. Phase I has space group P2₁2₁2₁, with Z = 4, a = 7.696(3), b = 13.2890(17) and c = 13.503(18) Å. The transition is both displacive and order-disorder involving mainly conformational changes of the organic chain [NH₃(CH₂)₅NH₃]²⁺ coupled with distortion of the TlCl₆ octahedra. This behaviour and the crystal dynamics will be discussed and compared with those found in the literature for homologous compounds.     

Resonant pumping far-infrared NH3 laser

A far-infrared (FIR) NH₃ laser was resonantly pumped with a line-tunable infrared (IR) NH₃ laser. The number of the observed FIR laser lines amounted to 33. Most of them belonged toaR(J,K) rotation-inversion transition in (0, 1, 0, 0) vibrational state. The line tunability of sealed-off FIR NH₃ laser was almost achieved in 90, 115, 150, and 220 m wavelength regions by the selective line tuning of the pumping IR NH₃ laser.     

CH3NH3I在制备CH3NH3PbI(3-x)Clx钙钛矿太阳能电池中的作用

利用具有钙钛矿结构的有机-无机杂化卤化物制备的太阳能电池, 由于具有溶液可加工性和高光电转换效率, 受到了广泛关注. 在目前报道的最高光电转换效率的器件中, 采用了CH₃NH₃PbI_(3-x)Cl_x碘氯混合钙钛矿作为吸光层, 据报道在这种材料中光电子的扩散长度可以超过1 μm. 本文综述了在CH₃NH₃PbI_(3-x)Cl_x方面现有的研究工作, 指出了薄膜制备条件的重要性, 并研究了CH₃NH₃I在PbCl₂/CH₃NH₃I热解法制备CH₃NH₃PbI_(3-x)Cl_x吸光层中的作用. 扫描电子显微镜研究表明CH₃NH₃I加入量为PbCl₂的2倍到2.75倍时, CH₃NH₃I加入量的增加可以提高CH₃NH₃PbI_(3-x)Cl_x吸光层的覆盖度和结晶度, CH₃NH₃I加入量进一步增加到3倍时, 形貌变化不大. X射线光电子能谱的数据证实了CH₃NH₃I加入量对覆盖度的影响, 并显示在CH₃NH₃I加入量大于PbCl₂的2.5倍以后, CH₃NH₃PbI_(3-x)Cl_x中氯的掺入量急剧下降. 光电测试表明器件性能随CH₃NH₃I加入量增加而增加, 在CH₃NH₃I/PbCl₂为3/1时达到最高, 加入量略小于3/1对性能影响不大.     

Intensities and line shapes in the v2-fundamentals of 14NH3 and 15NH3

Spectral transmission measurements in the v^s₂- and v^a₂-fundamentals of ¹⁴NH₃ and ¹⁵NH₃ have yielded information that is valuable in the interpretation of spectroscopic scans of Jupiter covering the thermal infrared between 9 and 12 μm. Our experimental data demonstrate that the absorption spectra of the two species of NH₃ differ from each other only in line positions but not in the strengths, widths or shapes of lines with the same quantum number designations.