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采用基于密度泛函理论的第一性原理方法和平板模型研究了CH3SH分子在Cu(111)表面的吸附反应.系统地计算了S原子在不同位置以不同方式吸附的一系列构型, 第一次得到未解离的CH3SH分子在Cu(111)表面顶位上的稳定吸附构型,该构型吸附属于弱的化学吸附, 吸附能为0.39 eV. 计算同时发现在热力学上解离结构比未解离结构更加稳定. 解离的CH3S吸附在桥位和中空位之间, 吸附能为0.75-0.77 eV. 计算分析了未解离吸附到解离吸附的两条反应路径, 最小能量路径的能垒为0.57 eV. 计算结果还表明S―H键断裂后的H原子并不是以H2分子的形式从表面解吸附而是以与表面成键的形式存在. 通过比较S原子在独立的CH3SH分子和吸附状态下的局域态密度, 发现S―H键断裂后S原子和表面的键合强于未断裂时S原子和表面的键合. 相似文献
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在超市无人结算服务中,使用电子标签对部分货物如水果、蔬菜等进行结算的成本过高、便捷性不高,至今依然采用人工结算的方式。针对这一问题,本文提出了基于卷积神经网络的食物识别方法。通过自建水果数据集来训练卷积神经网络分类模型;基于训练后的模型构建可视化平台进行食物识别。实验结果表明,利用卷积神经网络的食物识别的预测准确率为96.34%。 相似文献
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采用密度泛函理论的第一性原理方法研究了扶手椅型g-C3N4纳米带(AC-g-C3N4NRs)和锯齿型g-C3N4纳米带(ZZ-g-C3N4NRs)的电子结构和光学性质。结果表明:AC-g-C3N4NRs和ZZ-g-C3N4NRs的边缘H原子均能稳定存在。AC-g-C3N4NRs的价带顶主要由多数N原子贡献,而ZZ-g-C3N4NRs的价带顶主要由CH边缘附近的N原子贡献。AC-g-C3N4NRs的导带底主要属于纳米带一侧边缘或两侧边缘附近的C原子和N原子,而ZZ-g-C3N4NRs导带底主要属于ZZ-g-C3N4NRs的NH边缘附近的C原子和N原子。AC-g-C3N4NRs和ZZ-g-C3N4NRs的吸收系数和反射率都随纳米带宽度的增加而增加。随着AC-g-C3N4NR宽度的增加,吸收系数在低能区域产生明显的蓝移现象。 相似文献
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Faceting transitions in crystal growth and heteroepitaxial growth in the anisotropic phase-field crystal model 下载免费PDF全文
We modify the anisotropic phase-field crystal model(APFC),and present a semi-implicit spectral method to numerically solve the dynamic equation of the APFC model.The process results in the acceleration of computations by orders of magnitude relative to the conventional explicit finite-difference scheme,thereby,allowing us to work on a large system and for a long time.The faceting transitions introduced by the increasing anisotropy in crystal growth are then discussed.In particular,we investigate the morphological evolution in heteroepitaxial growth of our model.A new formation mechanism of misfit dislocations caused by vacancy trapping is found.The regular array of misfit dislocations produces a small-angle grain boundary under the right conditions,and it could significantly change the growth orientation of epitaxial layers. 相似文献
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Energetics and electronic structure of a single copper atomic chain wrapped in a carbon nanotube: a first-principles study 下载免费PDF全文
In the generalized gradient approximation, the energy and
electronic structure are investigated for a single copper atomic
chain wrapped in (4, 4), (5, 5) and (6, 6) armchair carbon nanotubes
by using the first-principles projector-augmented wave potential
within the framework of density functional theory. The results show
that the (4, 4) and (5, 5) tubes are too narrow to wrap a Cu chain,
but the (6, 6) tube is nearly ideal to wrap a Cu chain on its centre
axis. Wider tubes are anticipated to wrap more than one Cu
chain spontaneously with forces amounting to a fraction of a
nanonewton. Although the tube--chain interaction decreases with the
increase of the tube diameter of (4, 4), (5, 5) and (6, 6)
successively, the charge density of the Cu@(6, 6) combined system
still does not show complete superposition of that of the pristine (6, 6) tube and
Cu chain. Successively reducing the restrictions of (4, 4), (5,
5) and (6, 6) tubes on the Cu chain leads to a reduction in shift of the
highest peak of the Cu chain towards lower energies, that is from
-0.5177~eV of the isolated Cu chain to -1.36785~eV, -0.668~eV and
-0.588~eV for the Cu@(4, 4), Cu@(5, 5) and Cu@(6, 6) systems,
respectively. In reverse, the strong metallic character of the Cu chain
also enhances the metallic character of the combined systems so that
the broader pseudogaps of the pristine carbon nanotubes around the Fermi
level change into the narrow pseudogaps of the combined systems. 相似文献
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以绿色廉价的黑米为碳源,采用简单的水热法一步合成了碳点(carbon dots,CDs)。所合成的CDs不仅对pH、NaCl溶液和温度变化不敏感,并且不受多种金属离子的影响,表现出优异的稳定性。同时,CDs在较短波长范围(410~470 nm)表现出激发不依赖的发射行为,在较长波长范围(470~510 nm)又表现出弱激发依赖的发射行为。由于其优异的荧光特性、稳定性和低毒性,我们将其应用于人口腔角质形成细胞(Hok)、宫颈癌细胞(Hela)和骨髓间充质干细胞(MC3T3)的体外成像。 相似文献
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通过分析RLT码,针对RLT码译码算法中存在的缺陷,提出一种过滤式降维(FDR)算法,消除了传统译码算法在收到一定数量编码分组才开始解码的等待时间,实现了边接收边尝试解码的快速译码方式。此外,通过编码分组之间的异或运算,有效增加了度为1的编码分组的产生概率,不再仅依赖于从发送端获取度为1的编码分组,在降低传输时延的同时通过增加度为1的编码分组出现的概率从而提高译码成功率。在此基础上,提出一种与FDR译码算法相结合的优化度分布函数,适当提高度为2、度为3、度为4的编码分组的比例,从而大大增加一次降维即可得到度为1的编码分组的概率,加快了译码速度。NS3仿真结果表明,FDR算法的解码成功率普遍高于RLT码。 相似文献
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以绿色廉价的黑米为碳源,采用简单的水热法一步合成了碳点(carbon dots,CDs)。所合成的CDs不仅对pH、NaCl溶液和温度变化不敏感,并且不受多种金属离子的影响,表现出优异的稳定性。同时,CDs在较短波长范围(410~470 nm)表现出激发不依赖的发射行为,在较长波长范围(470~510 nm)又表现出弱激发依赖的发射行为。由于其优异的荧光特性、稳定性和低毒性,我们将其应用于人口腔角质形成细胞(Hok)、宫颈癌细胞(Hela)和骨髓间充质干细胞(MC3T3)的体外成像。 相似文献