Cubic protactinium hydrides are very important existing form in superconducting protactinium hydrogen series. In this work, the ground state structure and properties of cubic PaH<sub>3</sub> have been stud...Cubic protactinium hydrides are very important existing form in superconducting protactinium hydrogen series. In this work, the ground state structure and properties of cubic PaH<sub>3</sub> have been studied using the DFT + U method. This systematic study for two bulk properties includes the electronic structures, phonon dispersion curves, structural, mechanical and thermodynamic properties under the effective coulomb U and exchange J PBE + U parameters. Structural relaxation results show that the Pa-H and Pa-Pa distances in α-PaH<sub>3</sub> are significantly higher than that in β-PaH<sub>3</sub>, and the H-H distances in α-PaH<sub>3</sub> are slightly smaller than that in β-PaH<sub>3</sub>. For the ground state electronic structures of α-PaH<sub>3</sub> and β-PaH<sub>3</sub>, we found that α-PaH<sub>3</sub> and β-PaH<sub>3</sub> are metallic, and the protactinium 5f electronic states and hydrogen have obvious bonding effect, resulting in weakening of the material’s metallicity. This is consistent with observations for the other actinide hydrides such as ThH<sub>3</sub> and UH<sub>3</sub>. The phonon spectrum calculations reveal that the PBE and PBE + U methods give quite different frequencies for the optical branches of phonons of α-PaH<sub>3</sub> and β-PaH<sub>3</sub>. In addition, by including the vibrational entropy and the ZPE using the phonon frequencies obtained from the optimized unit cells we predict that the β-PaH<sub>3</sub> phase can not transit into α-PaH<sub>3</sub> phase above room temperature.展开更多
文摘Cubic protactinium hydrides are very important existing form in superconducting protactinium hydrogen series. In this work, the ground state structure and properties of cubic PaH<sub>3</sub> have been studied using the DFT + U method. This systematic study for two bulk properties includes the electronic structures, phonon dispersion curves, structural, mechanical and thermodynamic properties under the effective coulomb U and exchange J PBE + U parameters. Structural relaxation results show that the Pa-H and Pa-Pa distances in α-PaH<sub>3</sub> are significantly higher than that in β-PaH<sub>3</sub>, and the H-H distances in α-PaH<sub>3</sub> are slightly smaller than that in β-PaH<sub>3</sub>. For the ground state electronic structures of α-PaH<sub>3</sub> and β-PaH<sub>3</sub>, we found that α-PaH<sub>3</sub> and β-PaH<sub>3</sub> are metallic, and the protactinium 5f electronic states and hydrogen have obvious bonding effect, resulting in weakening of the material’s metallicity. This is consistent with observations for the other actinide hydrides such as ThH<sub>3</sub> and UH<sub>3</sub>. The phonon spectrum calculations reveal that the PBE and PBE + U methods give quite different frequencies for the optical branches of phonons of α-PaH<sub>3</sub> and β-PaH<sub>3</sub>. In addition, by including the vibrational entropy and the ZPE using the phonon frequencies obtained from the optimized unit cells we predict that the β-PaH<sub>3</sub> phase can not transit into α-PaH<sub>3</sub> phase above room temperature.
文摘为研究多芳环烃(PAHs)在虾夷马粪海胆Strongylocentrotus intermedius体内的富集动力学,系统认识其动力学参数特征,应用半静态双箱动力学模型拟合虾夷马粪海胆(壳直径2.0 cm±0.3 cm)对3,4-苯并[a]芘、9,10-二甲基蒽、3-甲基菲3种PAHs的生物富集过程,通过非线性拟合获得海胆对3种多环芳烃的吸收速率常数(K_1)、释放速率常数(K_2)、生物富集因子(BCF),以及平衡状态下海胆体内3种多环芳烃的含量(C_(max))、生物学半衰期(t_(1/2))等动力学参数。结果表明:海胆对3,4-苯并[a]芘富集动力学参数K_1、K_2、BCF、C_(max)、t_(1/2)的平均值分别为59.1、0.152、136.5、11.788μg/g和6.36 d;海胆对9,10-二甲基蒽富集动力学参数K_1,K_2、BCF、C_(max)、t_(1/2)的平均值分别为12.3、0.228、54.05、4.383μg/g和6.32 d;海胆对3-甲基菲富集动力学参数K_1、K_2、BCF、C_(max)、t_(1/2)的平均值分别为18.16、0.113、88.1、12.407μg/g和7.6 d;在5μg/L浓度条件下,海胆对3种多环芳烃的富集能力进行比较,依次为3,4-苯并[a]芘(14 d BCF=220)>3-甲基菲(14 d BCF=128.4)>9,10-二甲基蒽(14 d BCF=84.0)。研究表明,海胆对浓度为1、5、20μg/L的3,4-苯并[a]芘、浓度为5、100μg/L的3-甲基菲、浓度为5、10、50μg/L的9,10-二甲基蒽的生物富集过程均符合双箱动力学模型。
