Flexible Clusters Research Articles

An overview on copper based heterometallic complexes in combination with d10 metal ions derived from N2O2 donor di-Schiff base ligands

A good number of heterometallic complexes based on various Cu(II) bound “metalloligands” of N2O2 donor di-Schiff bases and some of their reduced counterpart along with group 12 metal ions have been synthesized and characterized by different research groups in the literature. This review focuses on an overview of the synthetic strategies, X-ray crystallographic structures and a few important properties of these complexes. These have been discussed in three major sub-classes: Cu(II)-Zn(II), Cu(II)-Cd(II) and Cu(II)-Hg(II) heterometallic complexes. Judicious combinations of carbonyls and di-amines in an easy and effective manner gives 14 selected di-Schiff base ligands (symmetrical and unsymmetrical) with particular shape, geometry and denticity that direct the synthesis of these metal complexes totally or preferentially towards di-, tri- or poly-nuclear entities. Moreover, owing to their ability to assemble three metal ions in close proximity, these resulting oxido-bridged flexible coordination clusters adapted to various other ligand functionalities with particular shape and sometimes unusual coordination modes with certain degree of control. Such unique structural aspect of this system is immensely important in inorganic synthesis. The inherent flexibility of the di-oxido bridged trinuclear coordination cluster led to produce isomeric linear and bent structures that usually depend upon various factors e.g. the nature of the Schiff base, anionic co-ligands, temperature, solvent etc. The structural aspects of resulting discrete and polymeric self-assemblies have enriched the coordination library that extended to develop numerous heterometallic systems with significant applications and new scopes

Flexible Hydrazone-Linked Metal-Covalent Organic Frameworks with Copper Clusters for Efficient Electrocatalytic Oxygen Evolution Reaction.

Despite the challenges associated with the synthesis of flexible metal-covalent organic frameworks (MCOFs), these offer the unique advantage of maximizing the atomic utilization efficiency. However, the construction of flexible MCOFs with flexible building units or linkages has rarely been reported. In this study, novel flexible MCOFs are constructed using flexible building blocks and copper clusters with hydrazone linkages. The heterometallic frameworks (Cu, Co) are prepared through the hydrazone linkage coordination method and evaluated as catalysts for the oxygen evolution reaction (OER). Owing to the spatial separation and functional cooperation of the heterometallic MCOF catalysts, the as-synthesized MCOFs exhibited outstanding catalytic activities with an overpotential of 268.8mV at 10mAcm-2 for the OER in 1 M KOH, which is superior to those of the reported covalent organic frameworks (COFs)-based OER catalysts. Theoretical calculations further elucidated the synergistic effect of heterometallic active sites within the linkages and frameworks, contributing to the enhanced OER activity. This study thus introduces a novel approach to the fundamental design of flexible MCOF catalysts for the OER, emphasizing their enhanced atomic utilization efficiency.

Consensus-Based Coordinated Control of Flexible Interconnected DC Microgrid Clusters

This paper proposes a consensus–coordinated control strategy to improve the stability and reliability of interconnected direct current (DC) microgrid cluster systems based on isolated bidirectional DC–DC converters. Compared with the traditional communication-based control strategy, the proposed method does not require an additional communication system. The proposed method is only based on local measurement information, making the whole cluster form an organic unit. No matter where the power disturbance occurs in the continuous-flow microgrid, all the balance units in the system can be linked to provide emergency power support for the disturbed microgrid, improve the dynamic characteristics of the DC voltage of the disturbed microgrid, and reduce the steady-state deviation of the DC voltage of the disturbed grid. The disturbance power is reasonably borne by the balance unit of the whole system according to its equivalent power distribution coefficient ratio. Finally, the effectiveness of the proposed control strategy is verified through the PSCAD/EMTDC simulation.

Recent processing of interaction mechanisms of single metallic atom/clusters in energy electrocatalysis

Understanding the interactions between single metallic atom/clusters (SMACs) has been taken to an unprecedented level, due to the delicate conditions required to produce exotic phenomena in electrode materials, such as thermocatalysis, electrocatalysis, and energy storage devices. Recently, state-of-the-art synthesis methods, such as one-step pyrolysis and multistep pyrolysis, have been developed for SMACs. Herein the interactions between SMACs such as synergetic, charge redistribution effects, and mutual assistance effects, are studied. SMACs have the advantage of maximum utilization of atoms and scattered active sites compared to single metal atoms, and they also have flexible and tunable atom clusters. SMACs have been widely developed and have shown excellent catalytic performance in electrocatalysis. Herein, the self-interaction between SMACs and their catalytic mechanisms are systematically described. The challenges in current synthesis strategies, catalytic mechanisms, and industrial applications of SMACs are analyzed, and a possible synthesis method for SMACs is proposed.

A Self-Adaptable Angular Based K-Medoid Clustering Scheme (SAACS) for Dynamic VANETs

Prior study suggests that VANET has two types of communications: Vehicle to Vehicle (V2V) and Vehicle to Infrastructure (V2I) communications. V2V is very important and ensures cooperative communications between vehicles and safety measures. It is also defined as Inter-Vehicle Communication (IVC).The communication is based on clustering the nodes to transmit the data from vehicle to vehicle. The overhead and stability are considered as main challenges that need to be addressed during vehicle intersections. In this paper, a novel self-adaptable Angular based k-medoid Clustering Scheme (SAACS) is proposed to form flexible clusters. The clusters are formed by estimating the road length and transmission ranges to minimize the network delay. And the Cluster Head (CH) is elected from a novel performance metric, ‘cosine-based node uncoupling frequency,’ that finds the best nodes irrespective of their current network statistics. The parametric analysis varies according to the number of vehicular nodes with the transmission range. The experimental results have proven that the proposed technique serves better in comparison to existing approaches such as Cluster Head Lifetime (CHL), Cluster Member Lifetime (CML), Cluster Number (CL), Cluster Overhead (CO), Packet Loss Ratio (PLR) and Average Packet Delay (APD). CHL is enhanced 40% as compare to Real-Time Vehicular Communication (RTVC), Efficient Cluster Head Selection (ECHS) whereas CML is 50% better than RTVC and ECHS. Packet loss ratio and overhead is 45% better in our proposed algorithm than RTVC and ECHS. It is observed from the results that the incorporation of cosine-based node uncoupling frequency has minimized the incongruity between vehicular nodes placed in dense and sparse zones of highways.

Research on scheduling strategy of heterogeneous flexible load clusters with strong association consider dual-scale similarities

With the background of multi-dimensional massive load data, the resource integration of heterogeneous flexible load is conducive to fully unlock its demand response potential. For the load aggregator scheduling scenario, this paper constructs a load management framework based on distributed clustering, and proposes a heterogeneous load cluster response strategy considering dual-scale similarity and strong correlation between clusters. First, in order to extract typical daily load curve of load cluster, a k-Shape algorithm based on the similarity criterion of shape is applied, and load amplitude constraint is introduced. The algorithm transforms the problem of centroid selection into optimization problem, which overcomes the limitation of traditional clustering algorithm in curve shape measurement. Then, the FP-growth algorithm is used to mine the correlation characteristics of heterogeneous load clusters in each scheduling time window. According to the strong correlation of each cluster in response potential, the response resources are further integrated to realize the combined scheduling among clusters. Finally, based on the measured data and simulation data, the proposed method is verified by simulation. The results show that this method improves the accuracy and detail description of clustering results, and the two heterogeneous clusters in the example have strong correlation in power consumption trend.

Application of the TEAC software for analysis of Energy Flexible Building Clusters – a case study

Nowadays, natural environment protection and sustainable development became common and necessary issues for all the economic sectors. It is extremely important to focus on all the efforts resulting in the most efficient and sustainable power sources and electric power grid. Typically, the residential districts are connected by electric grids, which with an application of the appropriate technologies might be considered as so-called smart-grids. In the smart-grid neighbourhoods, houses are the consumers, energy supply is performed by the local or/and national power plants, while energy distribution is performed using some monitoring and management systems. Such a residential area can be considered as a Building Cluster, the novel paradigm in the energy and environmental analysis of the built environments. In this article, the exemplary single-family houses neighbourhood is examined, following the Building Cluster paradigm. The analysed area is located in Lodz (Poland), consisting of 202 buildings. The study is performed by means of the home-developed software named TEAC (Tool for Energy Efficiency Analyses of an Energy Cluster). The analysis is focused on the energy, economic and environmental issues of the considered Building Cluster.

Flexible yard management in container terminals for uncertain retrieving sequence

With the booming traffic of global container transport, the container port throughput keeps increasing too. As the key node of the maritime network, the handling efficiency of container terminal always determine the efficiency of the whole container transport. In order to improve the handling efficiency of the container terminal, the optimization of yard space is still a challenge for terminal manager. Generally, the whole export block is used to be separated into several clusters to store export containers for different loading liners. In former studies, the unit of template generated is always fixed clusters like subblock, and the concept of flexible loading cluster is seldom touched. The application of flexible loading cluster, where the number of bays, rows and tiers can be changed based on service requirement, is discussed in this research. Thus this study wants to find out the optimal choice of flexible loading clusters and better solutions for export container allocation. A bi-objectives model which considers both the transportation distance and the handling congestions is built. A heuristic approach is developed to solve the real-life cases. We emphasize the possible rehandles during loading process and it is concluded that the application of flexible loading clusters is efficient for uncertain retrieving sequence.

General Cluster Sorption Isotherm

Abstract Adsorption isotherms are an essential tool in chemical physics of surfaces. However, several approaches based on a different theoretical basis exist and for some isotherms existing approaches can fail. Here, the sorbate-sorbate interaction is not limited to an orientation vertical to the adsorbent surface. Instead, a formal orientation-independent clustering, also comprising the possibility of multilayers as a special case, is underlain. The flexible clusters are described by classical thermodynamics including a free energy relationship depending on the cluster size. In this paper a rigorous unified treatment of the adsorbate-adsorbate-adsorbent interaction is shown to result in a general isotherm equation which is applied to literature data both concerning type IV isotherms of argon and nitrogen in ordered mesoporous silica, and type II isotherms of disordered macroporous silica. The new isotherm covers the full range of partial pressure (10−6 - 0.7). The determination of surface areas is not possible by this isotherm because the cross-sectional area of a cluster is unknown. Based on the full description of type IV isotherms, most known isotherms including BET are accessible by respective simplifications. The presented model is an extension of the classical derivation of the ζ-isotherm which was shown to describe type IV isotherms restricted to adsorbates with very strong tendency of clustering such as water on hydrophobic surface (Phys. Chem. Chem. Phys. 21 (2019) 5614).

Choice of loading clusters in container terminals

The storage allocation in the export yard of a container terminal determines the efficiency of container loading. Even if the yard manager has optimised the allocation of export containers to avoid rehandling, conflicts among loading quay cranes can still occur. Thus, all the possible handlings during loading must be considered when organising the yard space. In previous studies, the yard storage allocation has been assessed based on the subblock, which consists of several adjacent bays. However, to minimise all possible handlings in the loading process at the terminal, optimising more flexible storage clusters is also important. Thus, our aim in this research is to model the choice of loading clusters and derive a more flexible allocation strategy for organising the space in the export yard. A bi-objective model is built, which considers both the transportation distance and handling balance between blocks. A model aimed at minimising all possible handlings in the export yard for the loading process is also developed, and several of the insights derived can inform yard management in real-life operations. It is proven that the handling requirements have a significant effect on the choice of loading clusters, and yard managers should consider the various features of liner and loading processes when organising their storage space.

DNA-directed arrangement of soft synthetic compartments and their behavior in vitro and in vivo.

DNA has been widely used as a key tether to promote self-organization of super-assemblies with emergent properties. However, control of this process is still challenging for compartment assemblies and to date the resulting assemblies have unstable membranes precluding in vitro and in vivo testing. Here we present our approach to overcome these limitations, by manipulating molecular factors such as compartment membrane composition and DNA surface density, thereby controlling the size and stability of the resulting DNA-linked compartment clusters. The soft, flexible character of the polymer membrane and low number of ssDNA remaining exposed after cluster formation determine the interaction of these clusters with the cell surface. These clusters exhibit in vivo stability and lack of toxicity in a zebrafish model. To display the breadth of therapeutic applications attainable with our system, we encapsulated the medically established enzyme laccase within the inner compartment and demonstrated its activity within the clustered compartments. Most importantly, these clusters can interact selectively with different cell lines, opening a new strategy to modify and expand cellular functions by attaching such pre-organized soft DNA-mediated compartment clusters on cell surfaces for cell engineering or therapeutic applications.

Calculating the Symmetry Number of Flexible Sphere Clusters

We present a theoretical and computational framework to compute the symmetry number of a flexible sphere cluster in $\mathbb{R}^3$, using a definition of symmetry that arises naturally when calculating the equilibrium probability of a cluster of spheres in the sticky-sphere limit. We define the sticky symmetry group of the cluster as the set of permutations and inversions of the spheres which preserve adjacency and can be realized by continuous deformations of the cluster that do not change the set of contacts or cause particles to overlap. The symmetry number is the size of the sticky symmetry group. We introduce a numerical algorithm to compute the sticky symmetry group and symmetry number, and show it works well on several test cases. Furthermore we show that once the sticky symmetry group has been calculated for indistinguishable spheres, the symmetry group for partially distinguishable spheres (those with non-identical interactions) can be efficiently obtained without repeating the laborious parts of the computations. We use our algorithm to calculate the partition functions of every possible connected cluster of 6 identical sticky spheres, generating data that may be used to design interactions between spheres so they self-assemble into a desired structure.

Chemical signatures of surface microheterogeneity on liquid mixtures.

Many chemical reactions in Nature, the laboratory, and chemical industry occur in solvent mixtures that bring together species of dissimilar solubilities. Solvent mixtures are visually homogeneous, but are not randomly mixed at the molecular scale. In the all-important binary water-hydrotrope mixtures, small-angle neutron and dynamic light scattering experiments reveal the existence of short-lived (<50 ps), short-ranged (∼1 nm) concentration fluctuations. The presence of hydrophobic solutes stabilizes and extends such fluctuations into persistent, mesoscopic (10-100 nm) inhomogeneities. While the existence of inhomogeneities is well established, their impacts on reactivity are not fully understood. Here, we search for chemical signatures of inhomogeneities on the surfaces of W:X mixtures (W = water; X = acetonitrile, tetrahydrofuran, or 1,4-dioxane) by studying the reactions of Criegee intermediates (CIs) generated in situ from O3(g) addition to a hydrophobic olefin (OL) solute. Once formed, CIs isomerize to functionalized carboxylic acids (FC) or add water to produce α-hydroxy-hydroperoxides (HH), as detected by surface-specific, online pneumatic ionization mass spectrometry. Since only the formation of HH requires the presence of water, the dependence of the R = HH/FC ratio on water molar fraction expresses the accessibility of water to CIs on the surfaces of mixtures. The finding that R increases quasi-exponentially with in all solvent mixtures is consistent with CIs being preferentially produced (from their OL hydrophobic precursor) in X-rich, long-lived OL:X m W n interfacial clusters, rather than randomly dispersed on W:X surfaces. R vs dependences therefore reflect the average ⟨m, n⟩ composition of OL:X m W n interfacial clusters, as weighted by cluster reorganization dynamics. Water in large, rigid clusters could be less accessible to CIs than in smaller but more flexible clusters of lower water content. Since mesoscale inhomogeneities are intrinsic to most solvent mixtures, these phenomena should be quite general.

Study on the distribution characteristics of flexible filamentous particle clusters in a fluidized bed dryer

The inhomogeneity of gas-solid flow will affect the hydrodynamic characteristics and the performance of the fluidized bed. In this paper, the distribution of the flexible filamentous particle clusters was experimentally studied. Specifically, the influences of riser height, superficial gas velocity and bed inventory on the fluidization behavior and particle cluster distribution in the riser were discussed. Moreover, a new algorithm to optimize cluster identification was employed. Furthermore, cluster shape was analyzed by two parameters of spherical and wide aspect ratio index. Last but not least, the orthogonal photograph shooting method and PIV measurement were employed for obtaining more information on the flow of flexible filamentous particles. The results showed that the riser height, superficial gas velocity and bed inventory have profound influence on the distribution characteristics of particle clusters. This work can provide a very important reference for the drying process of flexible filamentous particles and lays a foundation for the analysis of heat and mass transfer in the future.

Impact of flexible bioenergy provision on residual load fluctuation: a case study for the TransnetBW transmission system in 2022

BackgroundThe transition towards a renewable based power system in Germany largely depends on variable renewable energy sources (vRES) like wind power and solar PV. Their high variability over time poses new challenges for power system stability. Bioenergy as a renewable source has already been established in recent years and has the capability to offset fluctuations from wind and solar PV and can therefore play a new role in coming years.MethodsThis paper describes how existing bioenergy plants can be operated in order to offset fluctuations in power systems, performing a power system modelling based on time series data. As sample transmission system (TS), TransnetBW has been chosen, one of the four German transmission systems. We modelled two different types of bioenergy plant clusters, one including solid biomass plants and the other cluster covering biogas plants and other plants with comparable characteristics. For the modelling of the operation of these clusters, we used registered time series of the years 2011 and 2012 for a total load and feed-in from wind and solar PV, which were projected for the year 2022. The flexible bioenergy clusters are operated in order to minimize fluctuations in residual load (RL). This approach served as the basis to assess how concepts for flexible bioenergy provision can contribute to the task of balancing future power systems based on vRES.ResultsBioenergy plays an important role in the renewable power supply of the TransnetBW TS, as it holds a share of 23.3% among the renewables projected for 2022. A flexible bioenergy (BE) provision allows for a reduction in daily residual load fluctuations by 30% compared to the non-flexible power generation from BE. Flexible BE effectively offsets high fluctuations originated from the feed-in of the substantial solar PV installations in the TS and also contributes to serve the peak load. But in contrast to regions with higher renewable shares from vRES, the amount of avoided BE power production in times of negative RL (excess power from renewables) is still negligible for the 2022 time frame investigated and thus reducing the immanent requirement for flexible BE.ConclusionsIn line with existing studies, the results show that bioenergy is already a valuable asset to achieve the targeted REN shares and can support the integration of the large vRES capacities in coming years, if produced flexibly. Operating biomass installations in a flexible manner effectively reduce daily fluctuations in RL, allow for a better integration of vRES and contribute to cover peak power demand. But from the findings of this case study, we conclude that the focus in the near-term should be on the efficient utilization of BE as the top priority until the demand for flexible BE provision is progressively increased with rising shares of vRES. Giving the regional differences, it should be stressed that the regional context, the relative share of wind and solar PV in the power system and therefore the investigated time horizon are important for defining the role of flexible bioenergy in the years to come.

Inhibitory Effect of Multivalent Rhamnobiosides on Recombinant Horseshoe Crab Plasma Lectin Interactions with Pseudomonas aeruginosa PAO1.

To evaluate the molecular interaction of recombinant horseshoe crab plasma lectin (rHPL) with Pseudomonas aeruginosa PAO1, multivalent rhamnobioside derivatives were designed. Eight rhamnoclusters with three or four α(1-3)-rhamnobiosides attached to different central cores, such as methyl gallate, pentaerythritol, and N-Boc Tris, through either an ethylene glycol or a tetraethylene glycol linker, were assembled in two consecutive azide-alkyne cycloaddition click reactions. The synthetic method embraced the preparation of two α(1-3)-rhamnobiosides with different linker arms and their conjugation, in stoichiometric or substoichiometric amounts, to propargyl ether-functionalized tri- or tetravalent scaffolds. A divalent derivative and two self-assembling rhamnobiosides were also prepared. The different architectures and valences of the rhamnoclusters provided an opportunity to evaluate the impact of topology and valency on the binding properties toward rHPL. Inhibitory ELISA data showed that all covalently linked rhamnoclusters could inhibit P. aeruginosa PAO1 recognition activity of rHPL with high efficacy. Trivalent rhamnobiosides showed a stronger inhibitory effect on P. aeruginosa PAO1 binding, and the more flexible clusters on a pentaerythritol or a Tris core were superior to the less flexible methyl gallate-based clusters. Interestingly, the length of the linker arms had a very low impact on the binding ability of the rhamnoclusters. Herein, the two trivalent derivatives on an N-Boc protected Tris central core were the best inhibitors. The self-assembling amphiphilic rhamnobioside derivatives were found to display no multivalent effect.

Moving Toward Zero Infrastructure Broadcasting

Is it reasonable to expect that broadcasting operations can occur with no on-premise infrastructure? This paper explores the necessary hardware and software configurations, cloud-based models, and on-demand coordination of necessary resources. Examples of the technologies and methodologies that will be discussed include services, network service orchestration, control of workflow applications, virtualized infrastructure and software applications, and the physical infrastructure layer. What, indeed, are some of the issues that are influencing these shifts in broadcasting operations and infrastructure deployments? One must only consider the nature of how consumers are accessing content on multiple devices, via Wi-Fi, in-home, and out-of-home, to obtain an indication of how much more complex broadcasting “television” has become. These new consumption realities have created a situation in which broadcast facilities are ill-equipped to ingest, transform, and distribute the multitude of formats and deliverables required. Today, it is standard fare to produce 100 different format types for a primetime television show. As a result of these new demands, a new method of facility architecture must be undertaken. This paper highlights the usage of flexible media clusters, software-defined networking and network function virtualization, OpenStack, packet media networking solutions to replace serial digital interface, software-defined storage, and resource reservation layers to elastically and dynamically provide a highly scalable allIP-based broadcasting architecture.

On energy efficient design for dynamic CoMP transmission in K-tier heterogeneous cellular networks

Motivated by the objective of pursuing revenue, improvement in coverage and reduction in energy cost for wireless communication networks have been of great significance for mobile operators. Therefore, heterogeneous cellular networks (HCNs) and Coordinated Multipoint (CoMP) transmission are considered as promising solutions to enhance the performances of wireless communication systems. This paper analyzed the K-tier HCNs with a dynamic downlink CoMP scheme, in which the flexible clusters of cooperative stations are determined by a connecting threshold 0. Using stochastic geometry, the coverage probability (CP) and energy efficiency (EE) of a K-tier HCN operating under this scheme are derived, based on which the trade-off between CP and EE is discovered and discussed. Simulation results show the validity of our derivations. The proposed schememay significantly reduce energy consumption sacrificing a small amount of CP, and outperforms the fixed scheme as well. The CP-EE trade-off are also revealed, whichsuggests suitable trade-off points between CP and EE that will deliver the maximum economic profitability. Tendencies discovered in this paper may provide the operators with opportunities for further optimization in pursuit of economic profitability.

Spiking neuro-fuzzy clustering system and its memristor crossbar based implementation

This study proposes a spiking neuro-fuzzy clustering system based on a novel spike encoding scheme and a compatible learning algorithm. In this system, we utilize an analog to binary encoding scheme that properly maps the concept of “distance” in multi-dimensional analog spaces to the concept of “dissimilarity” of binary bits in the equivalent binary spaces. When this scheme is combined with a novel binary to spike encoding scheme and a proper learning algorithm is applied, a powerful clustering algorithm is produced. This algorithm creates flexible fuzzy clusters in its analog input space and modifies their shapes to different convex shapes during the learning process. This system has plausible biological support due to its spike-based learning mechanism, its Quasi Spike Time Dependent Plasticity learning policy and its brain-like fuzzy clustering performance. Moreover, this neuro-fuzzy system is fully implementable on the hybrid memristor-crossbar/CMOS platform. The resultant circuit was simulated on one clustering task carried out in the binary input space on the Simon Lucas handwritten dataset and another clustering task carried out in the analog input space on Fisher׳s Iris standard dataset. The results show that it attained a higher clustering rate in comparison with other algorithms such as the Self Organizing Map, K-mean and the Spiking Radial Basis Function. The circuit was also successfully simulated on an image segmentation task and some clustering tasks performed in noisy spaces with various cluster sizes. Furthermore, the circuit variability analysis shows that device and signal variations up to 20% had no significant impact on the circuit׳s clustering performance, so the system is sufficiently immune to different variations due to its fuzzy nature.

Performance of M06, M06-2X, and M06-HF Density Functionals for Conformationally Flexible Anionic Clusters: M06 Functionals Perform Better than B3LYP for a Model System with Dispersion and Ionic Hydrogen-Bonding Interactions

We present a comparative assessment of the performance of the M06 suite of density functionals (M06, M06-2X, and M06-HF) against an MP2 benchmark for calculating the relative energies and geometric structures of the Cl(-)·arginine and Br(-)·arginine halide ion-amino acid clusters. Additional results are presented for the popular B3LYP density functional. The Cl(-)·arginine and Br(-)·arginine complexes are important prototypes for the phenomenon of anion-induced zwitterion formation. Results are presented for the canonical (noncharge separated) and zwitterionic (charge separated) tautomers of the clusters, as well as the numerous conformational isomers of the clusters. We find that all of the M06 functions perform well in terms of predicting the general trends in the conformer relative energies and identifying the global minimum conformer. This is in contrast to the B3LYP functional, which performed significantly less well for the canonical tautomers of the clusters where dispersion interactions contribute more significantly to the conformer energetics. We find that the M06 functional gave the lowest mean unsigned error for the relative energies of the canonical conformers (2.10 and 2.36 kJ/mol for Br(-)·arginine and Cl(-)·arginine), while M06-2X gave the lowest mean unsigned error for the zwitterionic conformers (0.85 and 1.23 kJ/mol for Br(-)·arginine and Cl(-)·arginine), thus providing insight into the types of physical systems where each of these functionals should perform best.