Search results for "Hybrid functional"
showing 10 items of 45 documents
Hybrid functional study of structural, electronic and magnetic properties of S-doped ZnO with and without neutral vacancy
2013
Abstract The structural and electronic properties of S-doped ZnO are investigated by density functional theory (DFT) and empirical pseudopotential method (EPM). Using the Heyd–Scuseria–Ernzerhof (HSE) hybrid functional with an adjusted mixing coefficient α , we obtain a good agreement on lattice parameters and band gap energy with the available experimental data. We have also investigate the Zn-vacancy effects on the electronic and magnetic properties of S-doped ZnO. Our calculations demonstrate that S impurity prefers to be close to the cation vacancy in the apical position. The magnetic analysis with the HSE functional shows a triplet state character with a total magnetic moment of 1.81 μ…
First principles calculations of the vibrational properties of single and dimer F-type centers in corundum crystals
2020
The present paper investigates the F-type centers in α-Al2O3 through their electronic and vibrational properties from first principle calculations using a periodic supercell approach, a hybrid functional, and all-electron Gaussian basis sets as implemented in the CRYSTAL17 code. Single F-type and dimer F2-type centers related to oxygen vacancies in various charge states were considered. The defect-induced vibrational modes were identified and found to appear mainly in the low (up to 300 cm-1) and high (above 700 cm-1) frequency regions, depending on the defect charge. The perturbation introduced by the defects to the thermal nuclear motion in the crystal lattice is discussed in terms of ato…
Theoretical and Experimental Study of (Ba,Sr)TiO 3 Perovskite Solid Solutions and BaTiO 3 /SrTiO 3 Heterostructures
2019
This study was supported by the ERA-NET HarvEnPiez project. The authors would like to thank their national funding agencies (Latvian State Education Development Agency, Slovenian Ministry of Higher Education, Science and Technology, Romanian National Authority for Scientific Research and Innovation, CCCDI-UEFISCDI, project number 49/2016 within PNCDI III – M-ERA NET Program).
Ab initio simulation of (Ba,Sr)TiO3 and (Ba,Ca)TiO3 perovskite solid solutions
2019
Abstract The results of ab initio (first-principles) computations of structural, elastic and piezoelectric properties of Ba(1−x)SrxTiO3 (BSTO) and Ba(1−x)CaxTiO3 (BCTO) perovskite solid solutions are presented, discussed and compared. Calculations are performed with the CRYSTAL14 computer code within the linear combination of atomic orbitals (LCAO) approximation, using advanced hybrid functionals of the density-functional-theory (DFT). Supercell model allows us to simulate solid solutions with different chemical compositions (x = 0, 0.125 and 0.25) within ferroelectric tetragonal phases (x
Theoretical Study on the Diffusion Mechanism of Cd in the Cu-Poor Phase of CuInSe2 Solar Cell Material
2013
We have employed first-principles static and molecular dynamics (MD) calculations with semilocal and screened-exchange hybrid density functionals to study the diffusion of Cd in bulk CuIn5Se8, a copper-poor ordered vacancy compound of CuInSe2. The diffusion mechanism and the underlying kinetics/energetics were investigated by combining ab initio metadynamics simulations and nudged elastic band (NEB) calculations. We found that the migration of Cd occurs via a kick-out of Cu atoms, assisted by the pristine vacancies that are constitutive of this compound, and follows a double-hump energy profile. The rate-limiting step has a barrier of about 1 eV at 0 K but reduces to 0.3 eV at 850 K, pointi…
First-principles calculations of iodine-related point defects in CsPbI3
2019
Many thanks to A. Lushchik, A. Popov and R. Merkle for numerous fruitful discussions. This study was partly supported by the Latvian Council for Science (grant LZP-2018/1-0147 to EK). R.A.E acknowledges the assistance of the University Computer Center of Saint-Petersburg State University for high-performance computations.
Understanding the optical and bonding properties of hybrid metal-halide (C5H16NP) PbX4 (X = Cl, Br, I) perovskite: A density-functional theory study
2021
Abstract Hybrid perovskites have demonstrated high stability and a promising optoelectronic performance for solar-cells. The quest over their functionalities beyond photo-voltaic applications is currently an important challenge. In this work, we have used density-functional theory to study hybrid perovskites. In particular, we have explored how atomic substitution could be used to design their optoelectronic properties. Under this approach, we have investigated the effect of changing the halogen atom (X = Cl, Br, I) on the structural, electronic, and optical properties of (C5H16NP) PbX4 hybrid perovskites. The electronic properties have been computed using hybrid functionals including the …
Interface-induced enhancement of piezoelectricity in the (SrTiO 3 ) m /(BaTiO 3 ) M−m superlattice for energy harvesting applications
2019
This research is funded by the Latvian Council of Science, project No. lzp-2018/1-0147. The computer resources were provided by Stuttgart Supercomputing Center (project DEFTD 12939) and Latvian Super Cluster (LASC). Many thanks to R. Dovesi, A. Erba, and M. Rérat for numerous stimulating discussions.
First-principles comparative study of perfect and defective CsPbX3 (X = Br, I) crystals
2020
We thank R. Merkle for numerous fruitful discussions and G. Siegle for experimental assistance. This study was partly supported by the M-ERA-NET project SunToChem (EK). Calculations were performed using computational facilities of St. Petersburg State University and Max Planck Institute for Solid State Research. Open Access funding provided by the Max Planck Society.
Hydrogen adsorption on the ZnO $(1\bar{1}00)$ surface: ab initio hybrid density functional linear combination of atomic orbitals calculations
2014
Hydrogen atoms unavoidably presented in ZnO samples or thin films during their synthesis considerably affect electrical conductivity. Results of first principles hybrid functional linear combination of atomic orbitals calculations are discussed for hydrogen atoms incorporated in bulk or adsorbed upon non-polar ZnO (1¯ 100) surfaces. The energy of H incorporation, atomic relaxation, electronic density redistribution and modification of the electronic structure are compared for both surface adsorption and bulk absorption. It is shown that hydrogen forms a strong bonding with the surface O ions (Eads = 2.7eV) whereas its incorporation into bulk is energetically quite unfavorable. Hydrogen adso…