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Single-point spin Chern number in a supercell framework 超级单体结构中的单点自旋陈数
IF 2.6 Q2 Physics and Astronomy Pub Date : 2023-01-06 DOI: 10.1088/2516-1075/acba6f
Roberta Favata, A. Marrazzo
We present an approach for the calculation of the Z2 topological invariant in non-crystalline two-dimensional quantum spin Hall insulators. While topological invariants were originally mathematically introduced for crystalline periodic systems, and crucially hinge on tracking the evolution of occupied states through the Brillouin zone, the introduction of disorder or dynamical effects can break the translational symmetry and imply the use of larger simulation cells, where the k-point sampling is typically reduced to the single Γ-point. Here, we introduce a single-point formula for the spin Chern number that enables to adopt the supercell framework, where a single Hamiltonian diagonalisation is performed. Inspired by the work of Prodan (2009 Phys. Rev. B 80 125327), our single-point approach allows to calculate the spin Chern number even when the spin operator sˆz does not commute with the Hamiltonian, as in the presence of Rashba spin–orbit coupling. We validate our method on the Kane–Mele model, both pristine and in the presence of Anderson disorder. Finally, we investigate the disorder-driven transition from the trivial phase to the topological state known as topological Anderson insulator. Beyond disordered systems, our approach is particularly useful to investigate the role of defects, to study topological alloys and in the context of ab-initio molecular dynamics simulations at finite temperature.
我们提出了一种计算非晶二维量子自旋霍尔绝缘体中Z2拓扑不变量的方法。虽然拓扑不变量最初是在数学上引入晶体周期系统的,并且关键取决于通过布里温区跟踪占位状态的演变,但引入无序或动态效应可能会打破平移对称性,并意味着使用更大的模拟单元,其中k点采样通常减少到单个Γ-point。在这里,我们引入了自旋陈恩数的单点公式,该公式能够采用超级单体框架,其中执行单个哈密顿对角化。受到Prodan(2009年物理学家)工作的启发。Rev. B 80 125327),我们的单点方法允许计算自旋陈恩数,即使自旋算符s * z不与哈密顿量交换,如在Rashba自旋轨道耦合存在的情况下。我们在Kane-Mele模型上验证了我们的方法,无论是原始的还是存在安德森紊乱的。最后,我们研究了无序驱动的从平凡相到拓扑状态的转变,即拓扑安德森绝缘子。除了无序系统之外,我们的方法对于研究缺陷的作用,研究拓扑合金以及在有限温度下从头算分子动力学模拟的背景下特别有用。
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引用次数: 4
QM-cluster model study of CO2 hydration mechanisms in metal-substituted human carbonic anhydrase II 金属取代人碳酸酐酶中CO2水化机理的qm -簇模型研究II
IF 2.6 Q2 Physics and Astronomy Pub Date : 2023-01-04 DOI: 10.1088/2516-1075/acb02c
Thomas J. Summers, Nathan J. DeYonker
Human carbonic anhydrase (CA) metalloenzymes utilize a Zn2+-containing active site to catalyze the interconversion of carbon dioxide to bicarbonate. The Zn2+ ion may be replaced with other divalent transition metals, though the catalytic efficiency of the enzyme will be reduced. In this work, quantum mechanical cluster models of the active site are used to map the reaction profile for the hydration mechanism of carbon dioxide. The Lipscomb proton transfer and Lindskog rotation mechanisms were examined for the native Zn2+-enzyme along with variants where the metal was substituted with Cd2+, Ni2+, Fe2+, and Fe3+. The findings highlight the impact the metal coordination geometry has on the reaction profile. The results also suggest Fe2+, which is the functional metal for a prototypical CA of an anaerobic bacterium, might also be functional for human CA if cultured within an anaerobic environment.
人碳酸酐酶(CA)金属酶利用含有Zn2+的活性位点催化二氧化碳转化为碳酸氢盐。Zn2+离子可以被其他二价过渡金属取代,尽管酶的催化效率会降低。在这项工作中,活性位点的量子力学簇模型被用于绘制二氧化碳水合机制的反应曲线。研究了天然Zn2+-酶的Lipscomb质子转移和Lindskog旋转机制,以及金属被Cd2+、Ni2+、Fe2+和Fe3+取代的变体。这些发现强调了金属配位几何结构对反应曲线的影响。结果还表明,Fe2+是厌氧细菌原型CA的功能金属,如果在厌氧环境中培养,它也可能对人类CA具有功能。
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引用次数: 1
Density-potential inversion from Moreau–Yosida regularization Moreau-Yosida正则化的密度势反演
IF 2.6 Q2 Physics and Astronomy Pub Date : 2022-12-24 DOI: 10.1088/2516-1075/acc626
M. Penz, M. Csirik, A. Laestadius
For a quantum-mechanical many-electron system, given a density, the Zhao–Morrison–Parr method allows to compute the effective potential that yields precisely that density. In this work, we demonstrate how this and similar inversion procedures mathematically relate to the Moreau–Yosida regularization of density functionals on Banach spaces. It is shown that these inversion procedures can in fact be understood as a limit process as the regularization parameter approaches zero. This sheds new insight on the role of Moreau–Yosida regularization in density-functional theory and allows to systematically improve density-potential inversion. Our results apply to the Kohn–Sham setting with fractional occupation that determines an effective one-body potential that in turn reproduces an interacting density.
对于一个量子力学的多电子系统,给定一个密度,Zhao-Morrison-Parr方法允许计算精确产生该密度的有效势。在这项工作中,我们展示了这种和类似的反演过程如何在数学上与Banach空间上密度泛函的Moreau-Yosida正则化相关联。结果表明,这些反演过程实际上可以理解为正则化参数趋近于零的极限过程。这为Moreau-Yosida正则化在密度泛函理论中的作用提供了新的见解,并允许系统地改进密度势反演。我们的结果适用于具有分数占位的Kohn-Sham设置,该设置决定了有效的单体势,从而再现了相互作用密度。
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引用次数: 3
A review of angle-resolved photoemission spectroscopy study on topological magnetic material family of MnBi2Te4 MnBi2Te4拓扑磁性材料家族角分辨光谱学研究综述
IF 2.6 Q2 Physics and Astronomy Pub Date : 2022-12-13 DOI: 10.1088/2516-1075/acab47
Zhicheng Jiang, Jiayu Liu, Zhengtai Liu, D. Shen
The MnBi2Te4 family compounds have drawn enormous attention in recent years due to their potential to realize the high-temperature quantum anomalous Hall effect. As one of the most direct techniques to probe electronic structure, angle-resolved photoemission spectroscopy (ARPES) has been widely applied to investigate the interplay between the magnetism and non-trivial topological band structure of MnBi2Te4 family materials. Here, we briefly review some of latest progress in ARPES study of MnBi2Te 4⋅ (Bi2Te3) (n = 0, 1, 2, 3) and analogous MnSb2Te 4⋅ (Sb2Te3)2 (n = 1, 2) series of materials. Aside from the direct observation of the non-trivial topological band structure, ARPES results reveal that their surface band gap can be well modulated by both temperature and Bi2Te3 interpolation. In addition, although ARPES results of the topological surface states are still under hot debate, the extensive experimental results have provided an opportunity to shed light on the complex interactions in intrinsic magnetic topological insulator.
近年来,MnBi2Te4家族化合物由于其实现高温量子反常霍尔效应的潜力而引起了人们的极大关注。作为探测电子结构最直接的技术之一,角分辨光电发射光谱(ARPES)已被广泛应用于研究MnBi2Te4族材料的磁性与非平凡拓扑能带结构之间的相互作用。在此,我们简要回顾了MnBi2Te 4·(Bi2Te3)(n=0,1,2,3)和类似的MnSb2Te 4·(Sb2Te3)2(n=1,2)系列材料的ARPES研究的一些最新进展。除了直接观察到非平凡拓扑能带结构外,ARPES结果还表明,温度和Bi2Te3插值都可以很好地调节它们的表面带隙。此外,尽管拓扑表面态的ARPES结果仍处于激烈的争论中,但广泛的实验结果为揭示本征磁性拓扑绝缘体中的复杂相互作用提供了机会。
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引用次数: 0
Local mode analysis of characteristic vibrational coupling in nucleobases and Watson–Crick base pairs of DNA DNA核碱基和沃森-克里克碱基对特征振动耦合的局域模式分析
IF 2.6 Q2 Physics and Astronomy Pub Date : 2022-12-09 DOI: 10.1088/2516-1075/acaa7a
Mateus M. Quintano, A. A. A. Delgado, Renaldo T. Moura Jr., M. Freindorf, E. Kraka
Two-dimensional infrared spectroscopy has reported highly delocalized in-plane base vibrations in the fingerprint region of nucleotide monophosphates, suggesting the involvement of base pair C=O and C=C ring bonds and considerable interaction between C=O bond stretches. The high delocalization results in congested vibrational spectra, which complicates the assignment of the peaks. This congestion also extends to Watson–Crick base pairs. We applied in this work the characterization of normal mode procedure, a special feature of our local mode analysis, and could for the first time identify the C=O and C=C bonds being engaged in base pair coupling and quantify their contribution to each of the delocalized fingerprint vibration. In addition, a detailed and quantitative description of the hydrogen bonds involved in the Watson–Crick base pairs was provided. Based on the results of this study, we developed a new protocol to elucidate on the assignment of bands in the vibrational spectra of nucleic acids by probing the vibrational space for specific interactions between functional groups prior to and upon base pairing. This protocol will aid to fill the gap between deoxyribonucleic acid structural information and vibrational spectroscopy experiments by facilitating the interpretation of spectra on a quantitative basis.
二维红外光谱已经报道了核苷酸单磷酸盐指纹区中高度离域的平面内碱基振动,表明碱基对C=O和C=C环键的参与以及C=O键伸展之间的相当大的相互作用。高离域导致拥挤的振动光谱,这使峰的分配复杂化。这种拥塞也延伸到Watson–Crick碱基对。我们在这项工作中应用了正态模式过程的表征,这是我们局部模式分析的一个特殊特征,并且可以首次识别参与碱基对耦合的C=O和C=C键,并量化它们对每个离域指纹振动的贡献。此外,还对Watson–Crick碱基对中涉及的氢键进行了详细和定量的描述。基于这项研究的结果,我们开发了一种新的方案,通过探测碱基配对之前和之后官能团之间的特定相互作用的振动空间,来阐明核酸振动光谱中谱带的分配。该方案将有助于填补脱氧核糖核酸结构信息和振动光谱实验之间的空白,促进光谱的定量解释。
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引用次数: 6
Computational evaluation of relevant species in inorganic sulfur biochemistry 无机硫生物化学中相关物质的计算评价
IF 2.6 Q2 Physics and Astronomy Pub Date : 2022-12-06 DOI: 10.1088/2516-1075/aca945
Juan Cruz Palermo, Jonathan A Córdova, J. Semelak, L. Capece, S. Bari, D. Estrin
The role of inorganic sulfur species in biological systems has gained considerable interest since the recognition of sulfanes, particularly dihydrogen sulfide or sulfane, H2S, disulfane, HSSH, trisulfane, HSSSH, and their conjugate bases, as endogenous species and mediators of signaling functions in different tissues. The one-electron oxidation of H2S/HS− has been assigned as the onset of signaling processes or oxidative detoxification mechanisms. These varied sulfur containing inorganic species are, together with organic counterparts, reunited as reactive sulfur species (RSS). In order to shed light on this rich and still not completely explored chemistry, we have performed electronic structure calculations at different levels of theory, to provide estimations and the molecular basis of the pKa values of the polysulfides HSSH and HSSSH and of the radical HS•. In addition, we also reported the characterization of selected inorganic RSS including both radical and non-radical species with different protonation states with the intention of assisting the interpretation of chemical/biochemical experiments involving these species.
无机硫在生物系统中的作用已经引起了相当大的兴趣,因为认识到磺胺类,特别是硫化氢二氢或磺胺、H2S、二磺酸、HSSH、三磺酸、HSSSH及其共轭碱,作为内源物种和不同组织信号功能的介质。H2S/HS−的单电子氧化被认为是信号过程或氧化解毒机制的开始。这些不同的含硫无机种类,与有机对应物一起,重新结合为活性硫种类(RSS)。为了揭示这种丰富而尚未完全探索的化学,我们在不同的理论水平上进行了电子结构计算,以提供多硫化物HSSH和HSSSH以及自由基HS•的pKa值的估计和分子基础。此外,我们还报道了选择性无机RSS的表征,包括具有不同质子化状态的自由基和非自由基物种,旨在帮助解释涉及这些物种的化学/生化实验。
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引用次数: 4
Efficient Kohn–Sham density-functional theory implementation of isotropic spectroscopic observables associated with quadratic response functions 有效的Kohn-Sham密度泛函理论实现与二次响应函数相关的各向同性光谱观测
IF 2.6 Q2 Physics and Astronomy Pub Date : 2022-12-02 DOI: 10.1088/2516-1075/aca859
Karan Ahmadzadeh, Xin Li, Ž. Rinkevičius, P. Norman
For general exchange–correlation functionals with a dependence on the local spin densities and spin-density gradients, we provide computationally tractable expressions for the tensor-averaged quadratic response functions pertinent to the experimental observables in second-harmonic generation (SHG). We demonstrate how the tensor-averaged quantities can be implemented with reference to a derived minimal number of first- and second-order perturbed Fock matrices. Our consideration has the capability of treating a situation of resonance enhancement as it is based on damped response theory and allows for the evaluation of tensor-averaged resonant-convergent quadratic response functions using only ∼25% (one-photon off-resonance regions) and ∼50% (one-photon resonance regions) of the number of auxiliary Fock matrices required when explicitly calculating all the needed individual tensor components. Numerical examples of SHG intensities in the one-photon off-resonance region are provided for a sample of makaluvamine derivatives recognized for their large nonlinear optical responses as well as a benchmark set of small- and medium-sized organic molecules.
对于依赖于局部自旋密度和自旋密度梯度的一般交换相关函数,我们提供了与二次谐波产生(SHG)实验观测值相关的张量平均二次响应函数的计算易于处理的表达式。我们证明了张量平均量是如何通过一阶和二阶微扰Fock矩阵的最小数量来实现的。我们的考虑具有处理共振增强情况的能力,因为它基于阻尼响应理论,并且允许在显式计算所有所需的单个张量分量时,仅使用所需辅助Fock矩阵数量的~ 25%(单光子非共振区)和~ 50%(单光子共振区)来评估张量平均共振收敛二次响应函数。本文提供了单光子非共振区SHG强度的数值例子,用于识别具有大非线性光学响应的makaluvamine衍生物样品以及一组中小型有机分子的基准。
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引用次数: 0
Theoretical and experimental insight into nano-optoelectronics 纳米光电子学的理论和实验见解
IF 2.6 Q2 Physics and Astronomy Pub Date : 2022-12-01 DOI: 10.1088/2516-1075/aca944
DattatrayJ. Late, S. Duhm
Dattatray J Late1,∗ and Steffen Duhm2,3,∗ 1 Centre for Nanoscience and Nanotechnology, Amity University Maharashtra, Mumbai-Pune Expressway, Bhatan, Post Somatne, Panvel, Mumbai, Maharashtra 410206, India 2 Institute of Functional Nano & Soft Materials (FUNSOM), Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, Suzhou 215123, People’s Republic of China 3 Jiangsu Key Laboratory of Advanced Negative Carbon Technologies, Soochow University, Suzhou 215123, People’s Republic of China ∗ Authors to whom any correspondence should be addressed.
1马哈拉施特拉邦Amity大学纳米科学与纳米技术研究中心,孟买-浦那高速公路,印度,孟买,马哈拉施特拉邦410206;2功能纳米与软材料研究所,苏州大学碳基功能材料与器件国际联合实验室,苏州215123;苏州大学,苏州215123,中华人民共和国*任何信件都应寄给作者。
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引用次数: 0
Convergence in determining enzyme functional descriptors across Kemp eliminase variants. 确定跨Kemp消除酶变体的酶功能描述符的收敛性。
IF 2.6 Q2 Physics and Astronomy Pub Date : 2022-12-01 DOI: 10.1088/2516-1075/acad51
Yaoyukun Jiang, Sebastian L Stull, Qianzhen Shao, Zhongyue J Yang

Molecular simulations have been extensively employed to accelerate biocatalytic discoveries. Enzyme functional descriptors derived from molecular simulations have been leveraged to guide the search for beneficial enzyme mutants. However, the ideal active-site region size for computing the descriptors over multiple enzyme variants remains untested. Here, we conducted convergence tests for dynamics-derived and electrostatic descriptors on 18 Kemp eliminase variants across six active-site regions with various boundary distances to the substrate. The tested descriptors include the root-mean-square deviation of the active-site region, the solvent accessible surface area ratio between the substrate and active site, and the projection of the electric field (EF) on the breaking C-H bond. All descriptors were evaluated using molecular mechanics methods. To understand the effects of electronic structure, the EF was also evaluated using quantum mechanics/molecular mechanics methods. The descriptor values were computed for 18 Kemp eliminase variants. Spearman correlation matrices were used to determine the region size condition under which further expansion of the region boundary does not substantially change the ranking of descriptor values. We observed that protein dynamics-derived descriptors, including RMSDactive_site and SASAratio, converge at a distance cutoff of 5 Å from the substrate. The electrostatic descriptor, EFC-H, converges at 6 Å using molecular mechanics methods with truncated enzyme models and 4 Å using quantum mechanics/molecular mechanics methods with whole enzyme model. This study serves as a future reference to determine descriptors for predictive modeling of enzyme engineering.

分子模拟已被广泛用于加速生物催化的发现。从分子模拟得到的酶功能描述符已经被用来指导寻找有益的酶突变体。然而,计算多个酶变体描述符的理想活性位点区域大小仍未经过测试。在这里,我们对18个Kemp消去酶变体的动态衍生和静电描述子进行了收敛测试,这些变体跨越6个与底物边界距离不同的活性位点区域。测试的描述符包括活性位点区域的均方根偏差,底物与活性位点之间的溶剂可及表面积比,以及电场(EF)在断裂C-H键上的投影。使用分子力学方法评估所有描述符。为了了解电子结构的影响,还使用量子力学/分子力学方法对EF进行了评估。计算了18个Kemp消除酶变体的描述符值。使用Spearman相关矩阵来确定区域大小条件,在该条件下,区域边界的进一步扩展不会实质性地改变描述符值的排序。我们观察到蛋白质动力学衍生的描述符,包括RMSDactive_site和SASAratio,在距离底物5 Å处收敛。在截断酶模型的分子力学方法下,静电描述子EFC-H收敛于6 Å,在全酶模型的量子力学/分子力学方法下收敛于4 Å。本研究为今后确定酶工程预测建模的描述符提供了参考。
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引用次数: 1
Computational investigations of the excited state dynamics and quenching mechanisms of polycyclic aromatic hydrocarbon DNA adducts in solution 溶液中多环芳烃DNA加合物激发态动力学和猝灭机制的计算研究
IF 2.6 Q2 Physics and Astronomy Pub Date : 2022-11-22 DOI: 10.1088/2516-1075/aca4ff
Solomon Yamoah Effah, W. Kaushalya, M. Hix, Alice R. Walker
Synthetically modified fluorescent nucleotides (SFNs) are highly popular in a variety of experiments to explore biochemistry in molecular imaging, but the connection between their photodynamics and quenching mechanisms to their molecular structure remain relatively unstudied computationally. We combine various levels of theory, including classical force field dynamics and excited state quantum mechanic/molecular mechanic Born–Oppenheimer dynamics to characterize a set of polycyclic aromatic hydrocarbon based substituents bound to cytidine (dC) and guanine (dG) nucleobases. We specifically focus on perylene (P) bound to C5 and C6 of dC, and the naturally occurring benzo[a]pyrene diol epoxide (B[a]PDE) on dG. We find that specific angles of the connection points between them modulate mechanisms of intramolecular charge transfer, where an electron moves from P to dC and dG to B[a]PDE once an optimal angle is reached. Functionalization location and flexibility of the substituent affect access to these angles and, therefore, the amount of rapid charge transfer quenching of the fluorescence that we observe. This work demonstrates that the choice of functionalization location for SFNs changes the accessibility of charge transfer mechanisms via steric hindrance, and suggest that this feature can be applied for future tuning of fluorescence properties.
合成修饰的荧光核苷酸(SFNs)在分子成像中探索生物化学的各种实验中非常受欢迎,但其光动力学和猝灭机制与其分子结构之间的联系在计算上仍然相对未研究。我们结合了不同水平的理论,包括经典力场动力学和激发态量子力学/分子力学Born–Oppenheimer动力学,来表征一组与胞苷(dC)和鸟嘌呤(dG)核碱基结合的多环芳烃基取代基。我们特别关注与dC的C5和C6结合的苝(P),以及dG上天然存在的苯并[a]芘二醇环氧化物(B[a]PDE)。我们发现,它们之间连接点的特定角度调节分子内电荷转移的机制,即一旦达到最佳角度,电子就从P移动到dC,从dG移动到B[a]PDE。取代基的官能化位置和柔性影响这些角度的获取,因此影响我们观察到的荧光的快速电荷转移猝灭的量。这项工作表明,SFNs功能化位置的选择通过空间位阻改变了电荷转移机制的可及性,并表明这一特征可用于未来荧光性质的调节。
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引用次数: 1
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Electronic Structure
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