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PUBLISHED ; Export Date: 5 January 2017 ; The energy gap of a molecular crystal is one of the most important properties since it determines the crystal charge transport when the material is utilized in electronic devices. This is, however, a quantity difficult to calculate and standard theoretical approaches based on density functional theory (DFT) have proven unable to provide accurate estimates. In fact, besides the well-known band-gap problem, DFT completely fails in capturing the fundamental gap reduction occurring when molecules are packed in a crystal structures. The failure has to be associated with the inability of describing the electronic polarization and the real space localization of the charged states. Here we describe a scheme based on constrained DFT, which can improve upon the shortcomings of standard DFT. The method is applied to the benzene crystal, where we show that accurate results can be achieved for both the band gap and also the energy level alignment. ; The authors are grateful to S. Refaely-Abramson for useful discussions. A.D. and I.R. were sponsored by the European Union through Project No. 618082 ACMOL. A.D. received additional support from the ?Ministerio de Economia y Com- petitividad? (Mineco) of Spain (Grant No. FPDI-2013-16641). S.S. acknowledges the Quest project funded by European Research Council. Computational resources were provided by the Trinity Centre for High Performance Computing (TCHPC) and the Irish Centre for High-End Computing (ICHEC)

The energy gap of a molecular crystal is one of the most important properties since it determines the crystal charge transport when the material is utilized in electronic devices. This is, however, a quantity difficult to calculate and standard theoretical approaches based on density functional theory (DFT) have proven unable to provide accurate estimates. In fact, besides the well-known band-gap problem, DFT completely fails in capturing the fundamental gap reduction occurring when molecules are packed in a crystal structures. The failure has to be associated with the inability of describing the electronic polarization and the real space localization of the charged states. Here we describe a scheme based on constrained DFT, which can improve upon the shortcomings of standard DFT. The method is applied to the benzene crystal, where we show that accurate results can be achieved for both the band gap and also the energy level alignment. ; A.D. and I.R. were sponsored by the European Union through Project No. 618082 ACMOL. A.D. received additional support from the "Ministerio de Economia y Competitividad" (Mineco) of Spain (Grant No. FPDI-2013-16641). S.S. acknowledges the Quest project funded by European Research Council. Computational resources were provided by the Trinity Centre for High Performance Computing (TCHPC) and the Irish Centre for High-End Computing (ICHEC). ; Peer reviewed

First principle calculations are performed to theoretically predict the physical properties of hexagonal aluminium arsenide planar and buckled monolayers. The structural characteristics showed that the buckled parameter is about 0.32 A°. Cohesive energies have favourable values and it indicates the fabrication possibility. Phonon dispersion properties indicated that the planar aluminium arsenic monolayers are dynamically unstable, while the buckled is less dynamically unstable. The elastic constant parameters achieved the required characteristics of stable hexagonal monolayer structures. The study of electronic band structure prefers to indirect semiconductor band gaps, and the density of states showed strong orbital hybridization in the conduction band. Planar structure has isotropic light electron effective mass and anisotropic heavy hole effective mass. The buckled structure has isotropic light electron effective mass and isotropic heavy hole effective mass. The absorption spectra have high absorption coefficient in various visible and ultraviolet wavelength. The absorption coefficient levels off at about direct and indirect band gaps.

10 páginas, 11 figuras.-- PACS number(s): 71.55.Eq, 75.75.Lf, 71.70.Gm ; We investigate the electronic and magnetic properties of (Ga,Mn)N nanocrystals using the density functional theory. We study both wurtzite and zinc-blende structures doped with one or two substitutional Mn impurities. For a single Mn dopant placed close to surface, the behavior of the empty Mn-induced state, hereafter referred to as "Mn hole," is different from bulk (Ga,Mn)N. The energy level corresponding to this off-center Mn hole lies within the quantum-dot gap near the conduction edge. For two Mn dopants, the most stable magnetic configuration is antiferromagnetic and this result was unexpected since (Ga,Mn)N bulk shows ferromagnetism in the ground state. The surprising antiferromagnetic alignment of two Mn spins is ascribed also to the holes linked to the Mn impurities that approach the surface. Unlike (Ga,Mn)N bulk, these Mn holes in confined (Ga,Mn)N nanostructures do not contribute to the ferromagnetic alignment of the two Mn spins. ; This work was supported by the Basque Government through the NANOMATERIALS project (Grant No. IE05-151) under the ETORTEK Program (iNanogune), the Spanish Ministerio de Ciencia y Tecnología of Spain (Grants No. TEC2007-68065-C03-03 and No. Fis2007- 66711-C02-02, and MONACEM project), and the University of the Basque Country (Grant No. IT-366-07). ; Peer reviewed

In this work we have implemented the fundamental-measure density functional theory due to Kierlik and Rosinberg to describe the adsorption of Lennard-Jones molecules in cylindrical pores. The accuracy of the theory in predicting adsorption isotherms and particle density profiles is checked by comparison with grand canonical Monte Carlo simulations for a wide range of pore sizes, showing very good agreement in all cases. In addition, the theory has been applied to the adsorption in slitlike pores to study the influence of the pore geometry on this property. The results indicate that the confinement of the cylindrical geometry introduces significant differences in the shape of the adsorption isotherms and density profiles. These differences are relevant for the characterization of porous materials. ; The authors thank Lev D. Gelb and Keith E. Gubbins for useful discussions. Alexander V. Neimark, Peter I. Ravikovitch, and Aleksey Vishnyakov are gratefully acknowledged for providing data for Fig. 10. This work was supported by the Spanish Government Ministerio de Ciencia y Tecnología (Grant Nos. PPQ2000-2888-E, PPQ2001-0671) and by URV (Project No. 2000PIR-21). S.F-G. thanks URV (Spain) and CONACyT (Me ́xico) for financial support. F.J.B. thanks the Universidad de Huelva and the Junta de Andalucía for financial support

A conference abstract from NIRItalia online 2021 in English and Italian. ; The authors gratefully acknowledge the European Commission for funding the InnoRenew project (grant agreement #739574) under the Horizon2020 Widespread-Teaming program and the Republic of Slovenia (investment funding of the Republic of Slovenia and the European Union European Regional Development Fund).

In silico-based optimization of Ir/P,S-catalysts for the asymmetric hydrogenation of unfunctionalized olefins using (E)-1-(but-2-en-2-yl)-4-methoxybenzene as a benchmark olefin has been carried out. DFT calculations revealed that the thioether group has a major role in directing the olefin coordination. This, together with the configuration of the biphenyl phosphite group, has an impact in maximizing the energy gap between the most stable transition states leading to opposite enantiomers. As a result, the optimized catalyst proved to be efficient in the hydrogenation of a range of alkenes with the same substitution pattern and olefin geometry as the benchmark olefin, regardless of the presence of functional groups with different coordination abilities (ee values up to 97%). Appealingly, further modifications at the thioether groups and at the biaryl phosphite moiety allowed the highly enantioselective hydrogenation of olefins with different substitution patterns (e.g., α,β-unsaturated lactones and lactams, 1,1′-disubstituted enol phosphinates, and cyclic β-enamides; ee values up to >99%). ; We gratefully acknowledge financial support from the Spanish Ministry of Science and Innovation (PID2019-104904GB-I00, PGC2018-100780-B-I00, and PGC2018-096616-B-I00), European Regional Development Fund (AEI/FEDER, UE), the Catalan Government (2017SGR1472), and the University of Alicante (VOGROB-316FI). M.B. also thanks the URV for generous support.