Papers by Patrizia Calaminici
Pd2 and CoPd dimers/N-doped graphene sensors with enhanced sensitivity for CO detection: A first-principles study
Journal of Molecular Modeling, Jul 17, 2023
Journal of Magnetism and Magnetic Materials, Aug 1, 2020
Electronic structure computations of pure Pd and Pd-based core-shell clusters were studied employ... more Electronic structure computations of pure Pd and Pd-based core-shell clusters were studied employing auxiliary density functional theory (ADFT). For this investigation icosahedral clusters with 13 and 55 atoms and octahedral clusters with 19 and 44 atoms were employed to analyze the change in the properties of the Pd and M@Pd core-shell clusters. All properties calculated for the M@Pd clusters are directly compared with the ones of pure palladium clusters. Spin multiplicities, spin magnetic moments, spin densities, binding energies per atom, segregation energies, and average bond lengths were calculated to understand their changes when varying the size, composition and shape of the M@Pd (M = Co, Ni, and Cu) core-shell clusters. The M 1 @Pd 12 and M 1 @Pd 18 (M = Co and Cu) clusters exhibit changes in the spin multiplicity and spin magnetic moment with respect to the Pd 13 and Pd 19 clusters, respectively, whereas the Ni 1 @Pd 12 and Ni 1 @Pd 18 clusters maintain the same properties as their pure Pd counterparts. The spin multiplicities and spin magnetic moments of the M 6 @Pd 38 and M 13 @Pd 42 (M = Co, Ni, and Cu) clusters greatly differ from their pure Pd counterparts. This study reveals that the Pd-Pd bond lengths are shorter in the M@Pd core-shell clusters compared to the ones of pure Pd clusters. This work demonstrates that the binding energy per atom of the M@Pd core-shell clusters is greater than the binding energy per atom of the pure Pd clusters. The calculated segregation energies indicate that 3d atoms prefer to be in the center of core-shell systems.
International Journal of Hydrogen Energy, Dec 1, 2016
A CoNi-decorated-Pt (40:40:20 wt%) electrocatalyst was theoretically studied and experimentally v... more A CoNi-decorated-Pt (40:40:20 wt%) electrocatalyst was theoretically studied and experimentally validated for the oxygen reduction reaction (ORR) in acid media. To predict the activity of the electrocatalyst a Co 16 Ni 16-decorated-Pt 3 cluster was employed. The O and O 2 adsorption energies were used as descriptors of the catalytic activity for the ORR. All calculations were performed using the density functional theory approach as implemented in the deMon2k code. A combined synthesis of high energy milling-galvanic displacement was performed to produce the CoNi-decorated-Pt electrocatalyst. The physical characterization of the electrocatalyst was developed using X-ray diffraction (XRD) for the phases identification, energy disperse X-ray spectroscopy (EDX) for compositional analysis and scanning transmission electron microscopy (STEM) to determine morphology and particle size of the synthesized electrocatalyst. Cyclic voltammetry and rotating disk electrode techniques were used for the electrochemical characterization of the synthesized electrocatalyst. The O and O 2 adsorption energies showed that CoNi-decorated-Pt (Co 16 Ni 16 ePt 3 cluster) electrocatalyst represents an attractive candidate for the ORR. STEM micrographs showed homogeneous nanocrystalline particles of 5e10 nm size. The CoNi-decorated-Pt nanoparticles presented high specific activity, 40% above of the determined from Pt/C and similar mass activity from the same commercial Pt/C, used as comparison. Electrochemical results confirm the feasibility of a combined synthesis method to produce nanocatalysts which exhibit similar catalytic activity than that of commercially available Pt/C electrocatalyst.
Transition Metal Clusters Polarizabilities
Trends and Perspectives in Modern Computational Science, 2006
First-principles investigation of adsorption and dissociation of molecular oxygen on pure Pd, Ni-doped Pd and NiPd alloy clusters
International Journal of Hydrogen Energy, Dec 1, 2017
Abstract A theoretical study on the adsorption of the molecular oxygen on the ground state struct... more Abstract A theoretical study on the adsorption of the molecular oxygen on the ground state structures of pure Pd n , Ni-doped Pd n−1 and Pd n/2 Ni n/2 (n = 4, 6, 8 and 10) clusters was performed. The dissociation pathways of the molecular oxygen on the Pd 4 , Pd 3 Ni and Pd 2 Ni 2 clusters were calculated. All calculations were performed using the auxiliary density functional theory (ADFT) approach as it is implemented in the deMon2k code. The objective of this work was to evaluate how the adsorption energy of the molecular oxygen is modified when the pure Pd clusters are doped with a Ni atom (Ni-doped Pd n−1 ) and when the composition of the Pd:Ni is 1:1 (Pd n/2 Ni n/2 ). Besides, the activation energy for the dissociation of the O 2 on the Pd 4 , Pd 3 Ni and Pd 2 Ni 2 clusters was calculated, too. Higher adsorption energies are found when the molecular oxygen is bound to two Ni atoms. Finally, the Ni-doped Pd 3 and Pd 2 Ni 2 clusters present lower activation energy compared to the one calculated for the pure Pd 4 cluster.
Stability and catalytic properties of Pt–Ni clusters supported on pyridinic N-doped graphene nanoflakes: an auxiliary density functional theory study
Theoretical Chemistry Accounts, Aug 22, 2022
Hybrid ADFT Study of the C<sub>104</sub> and C<sub>106</sub> IPR Isomers
Journal of Physical Chemistry A, Apr 25, 2019
This work presents a hybrid auxiliary density functional theory (ADFT) study of the neutral and h... more This work presents a hybrid auxiliary density functional theory (ADFT) study of the neutral and hexaanionic C104 and C106 fullerenes with the aim to determine their ground state structures. To this end, all C104 and C106 fullerene structures that obey the isolated pentagon rule (IPR) were optimized with the Perdew-Burke-Ernzerhof generalized gradient approximation followed by a single-point energy calculation with the PBE0 hybrid functional. Our studies show that this composite approach yields relative energies of giant fullerenes that are accurate to around 1 kcal/mol. As a result, the ground states of C104, C1046-, and C1066- can be assigned to the isomers 234:Cs, 821:D2, and 891:Cs, respectively. On the other hand, the energetically lowest lying IPR isomers of C106, 331:Cs, 1194:C2, 534:C1 are separated by less than 1 kcal/mol which makes an unequivocal ground state assignment by hybrid DFT methods impossible. To guide future experiments, we also report the simulated IR and Raman spectra of the most stable neutral and hexaanionic C104 and C106 fullerenes.
Journal of the American Chemical Society, Nov 23, 2007
Do we live in a 'braneworld'? A brane is four-dimensional time-like hypersurface; in a braneworld... more Do we live in a 'braneworld'? A brane is four-dimensional time-like hypersurface; in a braneworld model, the brane that is our Universe is embedded in a higher-dimensional spacetime bulk-a tantalizing representation of the extra dimensions that seem necessary in superstring theory, hence the popularity of the model for theoretical investigation. Hideki Maeda and colleagues have analysed the dynamics of a braneworld under 'Einstein-Gauss-Bonnet' gravity and discovered some interesting features, with links to current cosmological observations. EGB gravity includes the usual Einstein term plus a Gauss-Bonnet term-a combination of the Ricci scalar, Ricci tensor and Riemann tensor that arises naturally in superstring theory. Maeda et al. find that such a treatment produces a universe that does not have an initial singularity (the Big Bang), but rather a bounce. Moreover, there emerges the possibility of late-time acceleration, such as is indicated in recent observations and currently attributed to the existence of 'dark energy' .
Density functional calculations of molecular polarizabilities and hyperpolarizabilities
Journal of Chemical Physics, Nov 8, 1998
This paper presents dipole moments, static polarizabilities, first hyperpolarizabilities and seco... more This paper presents dipole moments, static polarizabilities, first hyperpolarizabilities and second hyperpolarizabilities calculated in the framework of density functional theory. All calculations have been performed using a finite field approach implemented in our new density functional theory program ALLCHEM. The calculations were of all-electron type. Both local and gradient-corrected functionals have been used. The influence of first- and second-order field-induced polarization functions, the external field strength, the numerical integration technique and the exchange-correlation functionals on the calculation of polarizabilities and hyperpolarizabilities is discussed in detail. A systematic study including 23 small and medium size molecules demonstrates that the obtained polarizabilities as well as the first and second hyperpolarizabilities are in good qualitative agreement with experimental data. The described density functional method provides polarizabilities and hyperpolarizabilities considerably better than the Hartree–Fock method and almost as accurate as much more expensive correlation treatments. This work demonstrates that reliable predictions of electro-optical properties for molecules with 20 and more atoms are possible using an efficient implementation of density functional theory.
Structures and properties of Co13−xCux (x=0–13) nanoclusters and their interaction with pyridinic N3-doped graphene nanoflake
Physica E-low-dimensional Systems & Nanostructures, Oct 1, 2021
Abstract The structures and properties of icosahedral Co13−xCux (x = 0–13) nanoclusters and their... more Abstract The structures and properties of icosahedral Co13−xCux (x = 0–13) nanoclusters and their interaction with pyridinic N 3 -doped graphene (PNG) nanoflake were studied using auxiliary density functional theory . First, the spin multiplicity, harmonic frequency, spin magnetic moment per atom, average bond length (ABL), vertical ionization potential (VIP), vertical electron affinity (VEA), and chemical hardness (η) of the icosahedral Co 13−xCux (x = 0–13) nanoclusters were investigated. Subsequently, the Co13−xCux (x = 0–13) nanoclusters were supported on PNG nanoflake and their interaction energies (Eint) and charge transfers were computed. The spin multiplicity and spin magnetic moment per atom decrease as the quantity of Co atoms diminishes in the Co13−xCux (x = 0–13) nanoclusters revealing that the magnetic behavior is dependent on the quantity of Co atoms in the Co13−xCux nanoclusters, whereas the ABL values raise as the number of Cu atoms increases in Co13−xCux (x = 0–13) nanoclusters. The Co9Cu4 and Co8Cu5 nanoclusters present the smallest η confirming the minor electronic stabilities for these systems. On the interaction between Co13−xCux (x = 0–13) nanoclusters and PNG nanoflake, charge transfer occurs from the nanoclusters to the PNG nanoflake. This study demonstrated that PNG nanoflake is an adequate material to stabilize the Co13−xCux (x = 0–13) nanoclusters.
International Journal of Hydrogen Energy, May 1, 2020
h i g h l i g h t s The O and OH adsorption energies were computed as predictors of the catalytic... more h i g h l i g h t s The O and OH adsorption energies were computed as predictors of the catalytic activity for the ORR. The stabilities of the M 6 @Pd 38 and M 6 @Pd 30 Pt 8 core-shell nanoclusters were investigated through segregation energy. The M 6 @Pd 38 core-shell nanoclusters present lower O adsorption energy with respect to the pure Pd 44 nanocluster. The following tendency of the ORR catalytic activity was found: Pt44 z M 6 @Pd 30 Pt 8 > M 6 @Pd 38 > Pd 44. The formation of core-shell structures is favored in the M 6 @Pd 38 and M 6 @Pd 30 Pt 8 (M ¼ Co, Ni, and Cu) systems.
Computing Letters, Mar 6, 2005
An extensive theoretical investigation of the nonpolar (101 0) and (112 0) surfaces as well as th... more An extensive theoretical investigation of the nonpolar (101 0) and (112 0) surfaces as well as the polar zinc-terminated ͑0001͒-Zn and oxygen-terminated (0001)-O surfaces of ZnO is presented. Particular attention is given to the convergence properties of various parameters such as basis set, k-point mesh, slab thickness, or relaxation constraints within local-density and generalized-gradient approximation pseudopotential calculations using both plane-wave and mixed-basis sets. The pros and cons of different approaches to deal with the stability problem of the polar surfaces are discussed. Reliable results for the structural relaxations and the energetics of these surfaces are presented and compared to previous theoretical and experimental data, which are also concisely reviewed and commented.
Assessment of BOMD simulations for the ground-state structure determination of transition metal clusters in the nanometer scale
Molecular Physics, Dec 21, 2015
ABSTRACT State-of-the art calculations have been performed for bimetallic transition metal cluste... more ABSTRACT State-of-the art calculations have been performed for bimetallic transition metal clusters such as Pd19M19 (M=Co and Ni) by employing the linear combination of Gaussian-type orbitals density functional theory (LCGTO-DFT) approach. Structures and energy properties were calculated for these clusters. For each cluster, several dozens of isomers were studied to determine the lowest energy structures. Initial structures for the geometry optimisation were taken along Born–Oppenheimer molecular dynamics (BOMD) trajectories, considering several spin multiplicities. All structures were fully optimised without any symmetry restriction. The optimised structures were characterised by vibrational analysis. Lowest energy structures, relative stability energy, harmonic frequencies, binding energies, vertical ionisation potential, vertical electron affinity and spin density plots are reported. The obtained results are compared with data from the literature. The ground-state structure topology is the same for both clusters. The Pd atoms decorate the surface of the core formed by either Co or Ni atoms. This work demonstrates the importance of using ab initio BOMD simulations to fully explore the potential energy surface of large transition metal clusters. Structure and spin multiplicity of the ground state structure of Pd19M19 (M=Co, Ni) clusters. Dark grey spheres correspond to Pd atoms and light green spheres correspond to either Co or Ni atoms, respectively.
Molecular Physics, Jun 20, 2001
Chalcones constitute an important group of natural products that in some cases possess different ... more Chalcones constitute an important group of natural products that in some cases possess different biological activities such as antimicrobial, anticancer and antiviral. Herein, we have used density functional theory (DFT) calculations (B3PW91/DGDZVP) to determine 13 C and 1 H nuclear magnetic resonance (NMR) chemical shifts for the two dihydrochalcones: 3,4,5-trimethoxydihydrochalcone and 2,3,4,4-tetramethoxydihydrochalcone. The experimental and theoretical NMR data were analyzed by simple linear regression and the more relevant parameters were selected. In additional, other statistical parameters (correlation coefficients, significance and predictability) were available to judge the quality of the calculations. Finally, the statistical analysis show good correlation experimental and theoretical NMR data with high predictive power.
QMLMaterial─A Quantum Machine Learning Software for Material Design and Discovery
Journal of Chemical Theory and Computation, Aug 15, 2023
<scp>GAMaterial</scp> —A genetic‐algorithm software for material design and discovery
Journal of Computational Chemistry, Nov 29, 2022
Automatic structural elucidation of vacancies in materials by active learning
Physical Chemistry Chemical Physics, 2022
The artificial intelligence method based on active learning for the automatic structural elucidat... more The artificial intelligence method based on active learning for the automatic structural elucidation of vacancies in materials. This is implemented in the quantum machine learning software/agent for material design and discovery (QMLMaterial).
A new active learning approach for adsorbate–substrate structural elucidation in silico
Journal of Molecular Modeling, Jun 1, 2022
Taking the multiplicity inside the loop: active learning for structural and spin multiplicity elucidation of atomic clusters
Theoretical Chemistry Accounts, Aug 1, 2021
Active learning (AL) has been successfully applied in materials science for the global optimizati... more Active learning (AL) has been successfully applied in materials science for the global optimization of clusters and defects in materials. Many important chemistry problems require the structural elucidation of molecules as a first step to the mechanistic elucidation of complex heterogeneous catalysis phenomena. Theoretical methods coupled with global optimization algorithms are successfully used for this purpose. However, it is challenging to find the global minimum structure together with the proper electronic spin multiplicity. In this work, we present an AL implementation for global optimization of atomic clusters where the spin multiplicity is considered in the search loop (SM@AL). The method was implemented in the QMLMaterial software, interfaced with the deMon2k program to perform local structure optimizations. In this work, we present applications of SM@AL for the global optimization, in terms of molecular structure and electronic spin of 3Al@Si11, where Si11 is doped by 3 Al, and Mo4C2 with spin multiplicities 2, 4 and 6 and 1, 3, 5, 7, 9 and 11, respectively.
RSC theoretical and computational chemistry series, 2021
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
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Papers by Patrizia Calaminici