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First-principles calculations based on density functional theory are performed to investigate the formation of titania/MXene composites taking (TiO2)5/M2C (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W) as cases of study. The present systematic analysis confirms a favorable, high exothermic interaction, which promotes important structural reconstructions of the (TiO2)5 cluster along with charge transfer from the MXene to titania. MXenes composed of d3 transition metals promote the strongest interaction, deformation energy, and charge transfer, followed by d4 and d5 M2C MXenes. We provide evidence that the formation of these (TiO2)5/M2C composites is governed by charge transfer, leading to scaling relationships. By using the electronegativity of the metal composing MXene and the MXene d-band center, we also establish linear correlations that can be used to predict the interaction strength of (TiO2)5/M2C composites just from the knowledge of the MXene composition. It is likely that the present trends hold for other TiO2/MXene composites. [ABSTRACT FROM AUTHOR]

First‐principles calculations on titania clusters (TiO2)n (n=5 and 10) supported on the pristine Ti2C (0001) surface were carried out to understand the properties of semiconductor/MXene composites with implications in (photo)‐catalysis. The reported results reveal a high exothermic interaction accompanied by a substantial charge transfer with a concomitant, notorious, deformation of the titania nanoclusters. The analysis of the density of states analysis of the composite systems evidences a metallic character with titania related states crossing the Fermi level. The picture of the chemical bonds is completed by the analysis of X‐Ray Photoelectron Spectra (XPS) features, evidencing clear shifts of the C(1s) and O(1s) related peaks relative to the isolated systems that have a quite complex origin. This detailed analysis provides insights to experimentalists interested in the design and synthesis of these systems with possible applications in catalysis. [ABSTRACT FROM AUTHOR]

A systematic computational study is presented aimed at accurately describing the electronic ground state nature and properties of M2C (M = Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W) MXenes. Electronic band structure calculations in the framework of density functional theory (DFT), carried out with different types of basis sets and employing the generalized gradient approach (GGA) and hybrid functionals, provide strong evidence that Ti2C, Zr2C, Hf2C, and Cr2C MXenes exhibit an open-shell conducting ground state with localized spins on the metal atoms, while V2C, Nb2C, Mo2C, Ta2C, and W2C MXenes exhibit a diamagnetic conducting ground state. For Ti2C, Zr2C, Hf2C, and Cr2C, the analysis of the low-lying spin polarized solutions with different spin orderings indicates that their ground states are antiferromagnetic (AFM), consisting of two ferromagnetic (FM) metal layers coupled antiferromagnetically. For the diamagnetic MXenes, the converged spin polarized solutions are significantly less stable than the closed shell solution except for the case of V2C and Mo2C where those excited open shell solutions can be thermally accessible (less than 300 meV per formula unit). The analysis of charge and spin density distributions of the ground state of the MXenes reveals that, in all cases, the metal atoms have a net charge close to +1 e and C atoms close to −2 e. In the case of diamagnetic MXenes, the electronic structure of V2C, Nb2C, and Ta2C is consistent with metal atoms exhibiting a closed-shell s2d2 configuration whereas for Mo2C, and W2C is consistent with a low-spin s1d4 configuration although the FM solution is close in energy for V2C and Mo2C suggesting that they may play a role in their chemistry at high temperature. For the open shell MXenes, the spin density primarily located at the metal atoms showing one unpaired electron per Ti+, Zr+, and Hf+ magnetic center, consistent with s2d1 configuration of the metal atom, and of ∼3.5 unpaired electrons per Cr+ magnetic center interpreted as a mixture of s2d3 and high-spin s1d4 configuration. Finally, the analysis of the density of states reveals the metallic character of all these bare MXenes, irrespective of the nature of the ground state, with significant covalent contributions for Mo2C and W2C. [ABSTRACT FROM AUTHOR]

Correction for 'The nature of the electronic ground state of M2C (M = Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W) MXenes' by Néstor García-Romeral et al., Phys. Chem. Chem. Phys., 2023, 25, 31153–31164, https://doi.org/10.1039/D3CP04402E. [ABSTRACT FROM AUTHOR]

First-principles density functional theory calculations are carried out on the (TiO 2 ) 5 cluster supported on the Ti 2 CT x (0001) surface with different chemical terminations, i.e. , -H, -O, and -OH, to study the interaction and understand the Ti 2 CT x functionalization effect on the formation of (TiO 2 ) 5 /Ti 2 CT x composites. Results show an exothermic interaction for all cases, whose strength is driven by the surface termination, promoting weaker bonds when the MXene is functionalized with H atoms. For Ti 2 CH 2 and Ti 2 C(OH) 2 MXenes, the interaction is accompanied by a charge transfer towards the titania cluster. All adsorptions are accompanied by a significant structural deformation of the titania nanocluster. The analysis of the density of states of (TiO 2 ) 5 /Ti 2 CH 2 and (TiO 2 ) 5 /Ti 2 C(OH) 2 composites shows a clear almost metallic character with titania-related states close to the Fermi level. However, for (TiO 2 ) 5 /Ti 2 CO 2 , the band positions are similar to those of a Type-I heterojunction. Overall, the MXene surface termination influence on the TiO 2 /MXene interaction is unveiled, providing more stable composite formations when the MXene surface is functionalized with -H and -OH groups, where the adsorption process is accompanied by significant charge transfer., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

First-principles calculations based on density functional theory are performed to investigate the formation of titania/MXene composites taking (TiO 2 ) 5 /M 2 C (M = Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W) as cases of study. The present systematic analysis confirms a favorable, high exothermic interaction, which promotes important structural reconstructions of the (TiO 2 ) 5 cluster along with charge transfer from the MXene to titania. MXenes composed of d 3 transition metals promote the strongest interaction, deformation energy, and charge transfer, followed by d 4 and d 5 M 2 C MXenes. We provide evidence that the formation of these (TiO 2 ) 5 /M 2 C composites is governed by charge transfer, leading to scaling relationships. By using the electronegativity of the metal composing MXene and the MXene d-band center, we also establish linear correlations that can be used to predict the interaction strength of (TiO 2 ) 5 /M 2 C composites just from the knowledge of the MXene composition. It is likely that the present trends hold for other TiO 2 /MXene composites.

A systematic computational study is presented aimed at accurately describing the electronic ground state nature and properties of M 2 C (M = Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W) MXenes. Electronic band structure calculations in the framework of density functional theory (DFT), carried out with different types of basis sets and employing the generalized gradient approach (GGA) and hybrid functionals, provide strong evidence that Ti 2 C, Zr 2 C, Hf 2 C, and Cr 2 C MXenes exhibit an open-shell conducting ground state with localized spins on the metal atoms, while V 2 C, Nb 2 C, Mo 2 C, Ta 2 C, and W 2 C MXenes exhibit a diamagnetic conducting ground state. For Ti 2 C, Zr 2 C, Hf 2 C, and Cr 2 C, the analysis of the low-lying spin polarized solutions with different spin orderings indicates that their ground states are antiferromagnetic (AFM), consisting of two ferromagnetic (FM) metal layers coupled antiferromagnetically. For the diamagnetic MXenes, the converged spin polarized solutions are significantly less stable than the closed shell solution except for the case of V 2 C and Mo 2 C where those excited open shell solutions can be thermally accessible (less than 300 meV per formula unit). The analysis of charge and spin density distributions of the ground state of the MXenes reveals that, in all cases, the metal atoms have a net charge close to +1 e and C atoms close to -2 e . In the case of diamagnetic MXenes, the electronic structure of V 2 C, Nb 2 C, and Ta 2 C is consistent with metal atoms exhibiting a closed-shell s 2 d 2 configuration whereas for Mo 2 C, and W 2 C is consistent with a low-spin s 1 d 4 configuration although the FM solution is close in energy for V 2 C and Mo 2 C suggesting that they may play a role in their chemistry at high temperature. For the open shell MXenes, the spin density primarily located at the metal atoms showing one unpaired electron per Ti + , Zr + , and Hf + magnetic center, consistent with s 2 d 1 configuration of the metal atom, and of ∼3.5 unpaired electrons per Cr + magnetic center interpreted as a mixture of s 2 d 3 and high-spin s 1 d 4 configuration. Finally, the analysis of the density of states reveals the metallic character of all these bare MXenes, irrespective of the nature of the ground state, with significant covalent contributions for Mo 2 C and W 2 C.

The nature of the electronic ground state of the Ti 2 C MXene is unambiguously determined by making use of density functional theory-based calculations including hybrid functionals together with a stringent computational setup providing numerically converged results up to 1 meV. All the explored density functionals (i.e., PBE, PBE0, and HSE06) consistently predict that the Ti 2 C MXene has a magnetic ground state corresponding to antiferromagnetic (AFM)-coupled ferromagnetic (FM) layers. A spin model, with one unpaired electron per Ti center, consistent with the nature of the chemical bond emerging from the calculations, is presented in which the relevant magnetic coupling constants are extracted from total energy differences of the involved magnetic solutions using an appropriate mapping approach. The use of different density functionals enables us to define a realistic range for the magnitude of each of the magnetic coupling constants. The intralayer FM interaction is the dominant term, but the other two AFM interlayer couplings are noticeable and cannot be neglected. Thus, the spin model cannot be reduced to include nearest-neighbor interactions only. The Néel temperature is roughly estimated to be in the 220 ± 30 K, suggesting that this material can be used in practical applications in spintronics and related fields., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)