arXiv subjects

Gerardo Martínez-Guajardo

Publications and source records attributed to Gerardo Martínez-Guajardo.

3 recordsLinked to original sources

arXiv2026

Unveiling AlSb as a Promising Zincblende Semiconductor for Visible-Light Shift-Current Generation

We use density functional theory to investigate the shift-current response in zincblende III--V (AlP, AlAs, AlSb, GaP, GaAs, InP, InAs, and InSb) and II--VI (ZnS, ZnSe, ZnTe, CdS, CdSe, and CdTe) semiconductors. Our main goal is to identify which material generates the largest shift-current under illumination and to examine the factors influencing this response. We find that aluminum-containing semiconductors, particularly AlSb, exhibit the highest shift-current responses, while CdSe shows the lowest. We analyze the contributions of specific band-to-band transitions to the shift-current in AlSb by selectively summing valence and conduction bands. Additionally, we calculate delocalization indices to investigate the electron delocalization, which correlates with the shift current. Hydrostatic pressure does not enhance the shift current in these materials. These findings have potential applications in optoelectronics and identify the most promising zincblende semiconductors for efficient shift-current generation under visible-light illumination

cond-mat.mtrl-sci↗

arXiv2022

Structures and stability of the Cu$_{38}$ cluster at finite temperature

The UV-visible and IR properties of the Cu$_{38}$ nanocluster depend to a great extent on the temperature. Density functional theory and nanothermodynamics can be combined to compute the geometrical optimization of isomers and their spectroscopic properties in an approximate manner. In this article, we investigate entropy-driven isomer distributions of Cu$_{38}$ clusters and the effect of temperature on their UV-visible and IR spectra. An extensive, systematic global search is performed on the potential and free energy surfaces of Cu38 using a two-stage strategy to identify the lowest-energy structure and its low-energy neighbors. The effects of temperature on the UV and IR spectra are considered via Boltzmann probability. The computed UV-visible and IR spectrum of each isomer is multiplied by its corresponding Boltzmann weight at finite temperature. Then, they are summed together to produce a final temperature-dependent, Boltzmann-weighted UV-visible and IR spectrum. Additionally, Molecular Dynamics simulation of the Cu$_{38}$ nanocluster was performed to gain insight into the system dynamics and make a three-dimensional movie of the system with atomistic resolution. Our results show the thermal populations at the absolute temperature of Cu38 cluster, and the disordered structure that dominates at high temperatures.

cond-mat.mtrl-sci↗

arXiv2021

Exploration of potential and free energy surfaces of the neutral Be$_4$B$_{8}$ chiral clusters and their stabilities at finite temperatures

The lowest-energy structure, distribution of isomers, and their molecular properties depend significantly on the geometry and temperature. The total energy computations under DFT methodology are typically carried out at zero temperature; thereby, entropic contributions to total energy are neglected, even though functional materials work at finite temperature. In the present study, the probability of occurrence of one particular Be$_4$B$_8$ isomer at temperature T is estimated within the framework of quantum statistical mechanics and nanothermodynamics. To locate a list of all possible low-energy chiral and achiral structures, an exhaustive and efficient exploration of the potential/free energy surface is done by employing a multilevel multistep global genetic algorithm search coupled to DFT. Moreover, we discuss the energetic ordering of structures computed at the DFT level against single-point energy calculations at the CCSD(T) level of theory. The computed VCD/IR spectrum of each isomer is multiplied by their corresponding Boltzmann weight at temperature T; then, they are summed together to produce a final Boltzmann weighted spectrum. Additionally, we present chemical bonding analysis using the Adaptive Natural Density Partitioning method in the chiral putative global minimum. The transition state structures and the enantiomer-enantiomer and enantiomer-achiral activation energies as a function of temperature, evidence that a change from an endergonic to an exergonic type of reaction occurs at a temperature of 739 K.

cond-mat.mtrl-sci↗