Structure and detonation performance of a novel HMX/LLM‐105 cocrystal explosive

Intermolecular interactions and properties of octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐ tetrazocine (HMX) / 2,6‐diamino‐3,5‐dinitropyrazine‐1‐oxide (LLM‐105) cocrystal were studied by using the dispersion‐corrected density functionals (ωB97XD, B97D) and meta‐hybrid functional (M062x) methods. Binding energies, heats of formation, thermodynamic properties, atoms in molecules, and natural bond orbital analysis were performed to investigate HMX/LLM‐105 complexes. Results show that the main intermolecular interactions between HMX and LLM‐105 are CH…O, NH…O, N…O, and O…O interactions. In addition, Monte Carlo simulation was employed to predict the crystal structure of HMX/LLM‐105 cocrystal. The HMX/LLM‐105 cocrystal is most likely to crystallize in C2/c space group, and its corresponding cell parameters are Z = 8, a = 41.63 Å, b = 6.77 Å, c = 45.63 Å, ß = 164.55°, and ρ = 1.99 g/cm³. Detonation velocity and pressure of HMX/LLM‐105 cocrystal are 8.95 km/s, 37.69GPa, a little lower than those of HMX (9.10 km/s, 37.76GPa). However, according to the net charges of nitro group, HMX/LLM‐105 cocrystal exhibits less sensitive than HMX. Finally, bond dissociation energy calculation shows that HMX/LLM‐105 complexes are thermally stable. Considering thermal stability, sensitivity, and detonation performance, HMX/LLM‐105 cocrystal meets the requirements of insensitive high energy density materials. Copyright © 2013 John Wiley & Sons, Ltd.     

The interaction of three fields in ECE theory: The inverse Faraday effect

The simultaneous interaction of three fundamental fields is illustrated in Einstein Cartan Evans (ECE) theory with reference to the effect of gravitation on the inverse Faraday effect. The three-field interaction in this case is that of the fermionic, electromagnetic and gravitational fields. The interaction of the first two is developed in a well-defined semi-classical approximation of the ECE wave equation and the effect of gravitation incorporated through the index reduced canonical energy momentum density T. The exercise is repeated using the ECE wave equations and a general rule developed for the effect of gravitation on the fermionic, electromagnetic weak and strong fields.     

Effect of microstructure on the coercivity of HDDR Nd-Fe-B permanent magnetic alloy

The effect of the grain boundary microstructure on the anisotropy and coercivity was investigated in an HDDR Nd-Fe-B permanent magnetic alloy. Considering the special microstructure of its magnetic powder grain, an anisotropic theoretical model influenced simultaneously by the structure defect at the grain boundary and the exchange coupling interaction was put forward. The variations of the structure defect factors based on the nucleation and pinning mechanism with 2r ₀/lex (where r ₀ and lex are the defect thickness and the length of exchange coupling, respectively) were calculated. The results show that the coercivity mechanism of an HDDR Nd-Fe-B permanent magnetic alloy is greatly related to its microstructure defect at the grain boundary. For a fixed lex, when 2r ₀/lex < 1.67, the coercivity is controlled by the pinning mechanism; when 2r ₀/lex > 1.67, it is determined by the nucleation mechanism. The coercivity reaches the maximum when 2r ₀/lex = 1.67. The calculation result is consistent well with the experimental result given by Morimoto et al. Supported by the National Natural Science Foundation of China (Grant No. 50671055)     

周期量级激光脉冲在不同密度的原子介质中传播行为的比较(英文)

利用不含慢变包络近似和旋波近似的全波Maxwell-Bloch方程组的数值解,研究了周期量级超短激光脉冲在Ladder型三能级原子介质中的传播行为并与在相应的稀疏介质中的情况进行了比较.我们发现,在传播过程中,超短脉冲在稠密介质中的时间演化规律与在稀疏介质中明显不同,而且这种差别将随初始脉冲面积的增大而加大.当初始脉冲面积较小时,在传播过程中,脉冲形状在稀疏介质中只有小的改变而在稠密介质中却有显著的变化.当初始脉冲面积足够大时,在稠密介质中在不同的传播距离处脉冲分裂为不同数量和形状的亚脉冲;在稀疏介质中脉冲形状在传播过程中仍然只有小的改变。产生以上差别的原因在于稠密原子介质中近偶极-偶极(NDD)相互作用导致的局域场修正(LFC)及比稀疏原子介质更强的极化电场的影响.其中,更强的极化电场的影响起着主要的作用,但局域场修正的作用也不能忽略,而极化电场的增强是由于原子密度的增加.     

磷化物三元混晶中电子-声子相互作用的维度和体积效应

考虑电子-声子耦合强度因维度而异,导出了描述三维、二维和一维混晶中电子-声子相互作用的哈密顿量。考虑构成三元混晶的两种二元晶体的晶格失配会使混晶体积随元素组分比改变,在推导三维、二维和一维三元混晶中极化子自陷能量和重整化有效质量时计入了离子相对位移与二元晶体原胞体积的关系。结果表明:磷化物三元混晶中极化子自陷能量和重整化有效质量随元素组分的变化关系呈明显的非线性特征,对晶格适配明显、电子-声子耦合较强的材料,体积效应不可忽略。维度越低,非线性特征和体积效应越明显。     

de Haas–van Alphen effect in strongly correlated electron systems

We present the Fermi surface properties in strongly correlated electron systems of rare earth and uranium compounds via de Haas–van Alphen experiments. The conduction electrons with large cyclotron effective masses over 100m₀ (m₀: rest mass of an electron) are detected in CeRu₂Si₂, CeCoIn₅ and UPt₃. These electrons move slowly in the crystal. The topology of the Fermi surface and the cyclotron mass are compared to those of energy band calculations.     

钙钛矿Mn基氧化物的电子顺磁共振行为的实验研究

借助电子顺磁共振技术,对Mn³⁺/Mn⁴⁺=2∶1和1∶1的两个典型体系 在居里温度T_C以上温区的顺磁行为进行了实验研究.实验表明,存在一特征温度 T_min,通过该温度将T_C以上的磁行为分成两个明显可区分的温区： 在T_min以上,共振谱由一对称的单线构成,Lande 因子g值与温度无关且接近 自由电子的值(～20023),线宽随温度呈线性变化等;而在T_{min关键词： 稀土锰氧化物 电子顺磁共振 交换变窄 自旋-自旋相互作用 自旋-晶格相互作用}     

The effect of oxygen vacancy on the oxide ion mobility in LaAlO3-based oxides

The electrical property of (La_1−xSr_x)_1−z(Al_1−yMg_y)O_3−δ (LSAM; x≤0.3, y≤0.15 and z≤0.1) was measured using the DC four-probe method as a function of temperature (500–1000°C) and oxygen partial pressure (1–10⁻²² atm). Among LSAMs, (La_0.9Sr_0.1)AlO_3−δ showed the highest ionic conductivity, σ_i=1.3×10⁻² S cm⁻¹ at 900°C. A simultaneous substitution at A and B sites or A site deficiency is expected to create larger oxygen vacancy and higher ionic conductivity. However, it showed a negative effect. The effect of the vacancy increase did not effect monotonously the ionic conductivity. It was found that the concentration of oxygen vacancy, [V_O], influences not only the oxide ion conductivity, σ_i, but also the mobility, μ_v, of [V_O]. These properties exhibit a maximum at around [V_O]=0.05. With the increase in [V_O], the activation energy, E_a, of the ionic conduction dropped from 1.8 to ca. 1.0 eV at [V_O]=0.05 and became almost constant at [V_O]>0.05. The dependency of the pre-exponential term, μ⁰_v, and E_a on [V_O] was analyzed and their effect on μ_v and σ_i was discussed with respect to crystal structure and defect association. It was estimated that the crystal structure mainly governs these properties. The effect of defect association could not be ignored but is considered to be a complicated correlation.     

Phonon frequency shift and effect of correlation on the electron-phonon interaction in heavy fermion systems

The electron-phonon interaction in the periodic Anderson model (PAM) is considered. The PAM incorporates the effect of onsite Coulomb interaction (U) between f-electrons. The influence of Coulomb correlation U on the phonon response of the system is studied by evaluating the phonon spectral function for various parameters of the model. The numerical evaluation of the spectral function is carried out in the long wavelength limit at finite temperatures keeping only linear terms in U. The observed behaviour is found to agree well with the general features obtained experimentally for some heavy fermion (HF) systems.     

双芯耦合光纤中高阶色散对光孤子相互作用的影响

利用变分原理对耦合纤芯中传输光孤子之间的相互作用和形成束缚孤子态的条件进行了研究，发现高阶色散减弱甚至可以消除光孤子之间的相互作用。这一结果为耦合光纤器件的设计提供了一种实用消除光孤子之间相互作用的方法。