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排序方式: 共有298条查询结果,搜索用时 15 毫秒
1.
通过改进Brezis和Merle的方法,结合Moser-Trudinger不等式,移动平面方法及比较原理,得到了方程-Q_Nu=f(u),u∈W_0~(1,N)(Ω)的正解的先验界,其中Ω是R~N中的一个有界光滑区域,非线性项f至多具有指数型增长. 相似文献
2.
Using the Laplace transform method, this paper deals with the Ulam stability of linear fractional differential equations with constant coefficients. 相似文献
3.
《中国化学快报》2021,32(10):3149-3154
In this paper, a novel BC3N2 monolayer has been found with a graphene-like structure using the developed particle swarm optimization algorithm in combination with ab initio calculations. The predicted structure meets the thermodynamical, dynamical, and mechanical stability requirements. Interestingly, the BC3N2 plane shows a metallic character. Importantly, BC3N2 has an in-plane stiffness comparable to that of graphene. We have also investigated the adsorption characteristics of CO2 on pristine monolayer and Mo functionalized monolayer using density functional theory. Subsequently, electronic structures of the interacting systems (CO2 molecule and substrates) have been preliminarily explored. The results show that Mo/BC3N2 has a stronger adsorption capacity towards CO2 comparing with the pristine one, which can provide a reference for the further study of the CO2 reduction mechanism on the transition metal-functionalized surface as well as the new catalyst’s design. 相似文献
4.
The synthesis of ammonia (NH3) through the electrochemical reduction of molecular nitrogen (N2) is a promising strategy for significantly reducing energy consumption compared to traditional industrial processes. Herein, we report the design of a series of monovacancy and divacancy defective graphenes decorated with single 3d transition metal atoms (TM@MVG and TM@DVG; TM=Sc−Zn) as electrocatalysts for the nitrogen-reduction reaction (NRR) aided by density functional theory (DFT) calculations. By comparing energies for N2 adsorption as well as the free energies associated with *N2 activation and *N2H formation, we successfully identified V@MVG, with the lowest potential of −0.63 V, to be an effective catalytic substrate for the NRR in an enzymatic mechanism. Electronic properties, including Bader charges, charge density differences, partial densities of states, and crystal orbital Hamilton populations, are further analyzed in detail. We believe that these results help to explain recent observations in this field and provide guidance for the exploration of efficient electrocatalysts for the NRR. 相似文献
5.
Theoretical prediction of the host–guest interactions between novel photoresponsive nanorings and C60: A strategy for facile encapsulation and release of fullerene 下载免费PDF全文
Kun Yuan Jing‐Shuang Dang Yi‐Jun Guo Xiang Zhao 《Journal of computational chemistry》2015,36(8):518-528
A series of photoresponsive‐group‐containing nanorings hosts with 12~14 Å in diameter is designed by introducing different number of azo groups as the structural composition units. And the host–guest interactions between fullerene C60 and those nanoring hosts were investigated theoretically at M06‐2X/6‐31G(d)//M06‐L/MIDI! and wB97X‐D/6‐31G(d) levels. Analysis on geometrical characteristics and host–guest binding energies revealed that the designed nanoring molecule (labeled as 7 ) which is composed by seven azo groups and seven phenyls is the most feasible host for encapsulation of C60 guest among all candidates. Moreover, inferring from the simulated UV‐vis‐NIR spectroscopy, the C60 guest could be facilely released from the cavity of the host 7 via configuration transformation between trans‐form and cis‐form of the host under the 563 nm photoirradiation. Additionally, the frontier orbital features, weak interaction regions, infrared, and NMR spectra of the C60@7 host–guest complex have also been investigated theoretically. © 2015 Wiley Periodicals, Inc. 相似文献
6.
7.
Zhi‐Feng Li Yuan‐Cheng Zhu Guo‐Fang Zuo Hui‐An Tang Hong‐Yü Li 《International journal of quantum chemistry》2011,111(3):570-577
A novel single‐electron sodium bond system of H3C···Na? H (I), H3C···Na? OH(II), H3C···Na? F(III), H3C···Na‐CCH(IV), H3C···Na? CN (V) and H3C···Na? NC (VI) complexes has been studied by using MP2/6‐311++G** and MP2/aug‐cc‐pVTZ methods for the first time. We demonstrated that the single‐electron sodium bond H3C···Na? Y formed between H3C and Na? Y (Y?H, OH, F, CCH, CN, and NC) could induce the Na? Y increased and stretching frequencies of I–IV and VI are red‐shifted, including the Na? N bond in complex V is blue‐shifted abnormally. The interaction energies are calculated at two levels of theory [MP2, CCSD(T)] with different basis. The results shows that the strength of binding bond in group 2 (IV–VI) with π electrons are stronger than that of group 1 (I–III) without π electrons. For all complexes, the main orbital interactions between moieties H3C and Na? Y are LP1(C)→LP*1(Na). By comparisons with some related systems, it is concluded that the strength of single‐electron bond is increased in the order: hydrogen bond < bromine bond < sodium bond < lithium bond. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
8.
The two-state reaction mechanism of the Pt4+/− with N2O (CO) on the quartet and doublet potential energy surfaces has been investigated at the B3LYP level. The effect of Pt4
− anion assistance is analyzed using the activation strain model in which the activation energy (ΔΕ
≠) is decomposed into the distortion energies
(\Updelta E 1 \textdist ) (\Updelta E^{ \ne }_{\text{dist}} ) and the stabilizing transition state (TS) interaction energies
(\Updelta E 1 \textint ) (\Updelta E^{ \ne }_{\text{int}} ) , namely
\Updelta E 1 = \Updelta E 1 \textdist + \Updelta E 1 \textint \Updelta E^{ \ne } = \Updelta E^{ \ne }_{\text{dist}} + \Updelta E^{ \ne }_{\text{int}} . The lowering of activation barriers through Pt4
− anion assistance is caused by the TS interaction
\Updelta E 1 \textint \Updelta E^{ \ne }_{\text{int}} (−90.7 to −95.6 kcal/mol) becoming more stabilizing. This is attributed to the N2O π*-LUMO and Pt d HOMO back-donation interactions. However, the strength of the back-donation interactions has significantly
impact on the reaction mechanism. For the Pt4
− anion system, it has very significant back-bonding interaction (N2O negative charge of 0.79e), HOMO has 81.5% π* LUMO(N2O) character, with 3d orbital contributions of 10.7% from Pt(3) and 7.7% from Pt(7) near the 4TS4 transition state. This facilitates the bending of the N2O molecule, the N–O bond weakening, and an O−(2P) dissociation without surface crossing. For the Pt4
+ cation system, the strength of the charge transfer is weaker, which leads to the diabatic (spin conserving) dissociation
of N2O: N2O(1∑+) → N2(1∑g+) + O(1D). The quartet to doublet state transition should occur efficiently near the 4TS1 due to the larger SOC value calculated of 677.9 cm−1. Not only will the reaction overcome spin-change-induced barrier (ca. 7 kcal/mol) but also overcome adiabatic barrier (ca.
40.1 kcal/mol).Therefore, the lack of a thermodynamic driving force is an important factor contributing to the low efficiency
of the reaction system. 相似文献
9.
YUAN Kun- ZUO GuoFang LIU YanZhi ZHU YuanCheng LIU XinWen & ZHANG JunYan Key Laboratory for New Molecule Design Function of Gansu Education Department College of Life-Science Chemistry Tianshui Normal University Tianshui China State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou China 《中国科学B辑(英文版)》2011,(1)
The optimized geometries of the three complexes between MeHn (Me=Na,Mg,Be;n=1 or 2) and SiH4 have been calculated at the B3LYP/6-311++g**,MP2/6-311++g(3df,3pd) and MP2/aug-cc-pvtz levels,respectively.The red-shift inverse hydrogen bonds (IHBs) based on Si-H,an electron donor,were reported.The calculated binding energies with basis set super-position error (BSSE) correction of the three complexes are-5.98,-8.65 and-3.96 kJ mol-1 (MP2/6-311++g(3df,3pd)),respectively,which agree with the results obtained via M... 相似文献
10.