分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Terahertz vibrational spectroscopy has recently been demonstrated as a novel noninvasive technique for the characterization of biological molecules. But the interpretation of the experimentally measured terahertz absorption bands requires robust computational method. In this paper, we present a statistical method for predicting the absorption peak positions of a macromolecule in the terahertz region. The essence of this method is to calculate the absorption spectra of a biological molecule based on multiple short scale molecular dynamics trajectories instead of using a long time scale trajectory. The method was employed to calculate the absorption peak positions of the protein, thioredoxin from Escherichia coli (E.coli), in the range of 1025 cm1 to verify the reliability of this statistical method. The predicted absorption peak positions of thioredoxin show good correlation with measured results demonstrating that the proposed method is effective in terahertz absorption spectra modeling. Such approach can be applied to predict characteristic spectral features of biomolecules in the terahertz region.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Molecular dynamics simulation was performed to investigate the effect of thickness on the properties and struc- ture of ultrathin tetrahedral amorphous carbon films (ta-C). The present simulation showed that both the density and residual compressive stress decreased with increasing the thickness of ultrathin ta-C films, which was in agreement with the experimental results. The gradient of properties with the thickness was dependent on the incident kinetic energy of deposited atoms; when the incident kinetic energy was 10 eV/atom, the slower gradient was observed. Further structural analysis indicated that the critical relaxation of highly distorted bond angles was responsible for the reduction of residual compressive stress in the films deposited at 10 eV/atom, while the joint relaxation of both the distorted bond angles and C\C bond length led to the fast release of residual compressive stress in the films deposited at 70 eV/atom.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Amorphous carbon films (a-C) codoped by two metal elements exhibit the desirable combination of tribological and mechanical properties for widely potential applications, but are also prone to catastrophic failure due to the inevitable residual compressive stress. Thus far, the residual stress reduction mechanism remains unclear due to the insufficient understanding of the structure from the atomic and electronic scale. In this paper, using ab initio calculations, we first designed a novel Cu/Cr codoped a-C film and demonstrated that compared with pure and Cu/Cr monodoped cases, the residual stress in Cu/Cr codoped a-C films could be reduced by 93.6% remarkably. Atomic bond structure analysis revealed that the addition of Cu and Cr impurities in amorphous carbon structure resulted in the critical and significant relaxation of distorted C−C bond lengths. On the other hand, electronic structure calculation indicated a weak bonding interaction between the Cr and C atoms, while the antibonding interaction was observed for the Cu−C bonds, which would play a pivot site for the release of strain energy. Those interactions combined with the structural evolution could account for the drastic residual stress reduction caused by Cu/Cr codoping. Our results provide the theoretical guidance and desirable strategy to design and fabricate a new nanocomposite a-C films with combined properties for renewed applications.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Nitrogen-doped diamond-like carbon (N-DLC) films were synthesized by glow discharge plasma enhanced chemical vapor deposition (PECVD) using a hybrid ion beam system. The influence of nitrogen incorporation on the microstructure and electrochemical properties of N-DLC films was investigated by scanning probe microscopy, Raman spectroscopy, X-ray photoemission spectroscopy and cycle voltam- metry. Regardless of the deposition parameters, the surface of all the deposited films is very smooth. Raman spectra show that ID/IG increases from 0.6 to 1.04 with the substrate bias voltage increases. XPS results identify that carbon is bonded with nitrogen and the substrate bias makes no distinct contribution to the N content in the films, even the N-DLC film at bias of −550 V has the lowest N–O bonds concen- tration and the highest C–N bonds concentration. The film electrodes show the wide potential windows range over 4 V, lower background currents in strong acid media. At the bias of −550 V, the N-DLC film electrode not only exhibits the Ep at 209 mV and Iox /Ired at 0.8778 in K3 Fe(CN)6 solution, respectively, pp but also illustrates a nearly reversible electrode reaction. The mechanism of electroproperties is discussed in terms of the atomic bond structures and diffusion process.
提交时间: 2017-05-02
摘要: Here, we selected Ti, Cr, and Was the representative metal elements to composite with Al atom in order to generate co-doped amorphous carbon [a-C] films using ab initio calculations. Results show that compared with the pure and mono-doped cases, the Ti/Al
提交时间: 2017-05-02
摘要: Cu-containing diamond-like carbon [Cu-DLC] films were deposited on Si/glass substrate by a hybrid ion beam deposition system. The Cu concentration [0.1-39.7 at.%] in the film was controlled by varying the sputtering current. The microstructure and composi
提交时间: 2017-05-02
摘要: V2AlC belongs to a family of ternary nano-laminate alloys known as the MAX phases, which exhibit a unique combination of metallic and ceramic properties. In this work V-Al-C coatings with deposited [V, Al][2]C nano-crystallines and amorphous phase were ma