Browsing by Author "Wang, Xiaotian"

Now showing 1 - 7 of 7

Citation - WoS: 8
Citation - Scopus: 8
Complex Nodal Structure Phonons Formed by Open and Closed Nodal Lines in Coass and Na₂cup Solids
(Royal Soc Chemistry, 2022) Ding, Guangqian; Sun, Tingting; Surucu, Gokhan; Surucu, Ozge; Gencer, Aysenur; Wang, Xiaotian
Topological phononic states with nodal lines not only have updated our knowledge of the phases of matter in a fundamental way, but also have become a major frontier research direction in condensed matter physics. From a mathematical perspective, nodal line phonons can be divided into open and closed types. The present attempt is a report on the coexistence of such open and closed nodal line phonons in two realistic solids, CoAsS and Na2CuP, based on first-principles calculations. Furthermore, it is shown that the closed and the open nodal line states in CoAsS and Na2CuP have touching points and can form a complex nodal structure phonon in a momentum space. Due to the topologically non-trivial behavior of the complex nodal structure in both phonons, evident phononic surface states occur in the projected surfaces of both materials. In this way, these states, arising from the projected crossing points, can benefit experimental detection in follow-up studies. It has been stated that the open and closed nodal line states are formed by the crossings of two phonon branches and, hence, these two types of nodal line phonons are coupled with each other. The results obtained here could be considered as a breakthrough in clearly demonstrating the coexistence of the open and closed nodal line states in phonons and, for this reason, may inspire researchers seeking materials with such topological states in other bosons, such as photons.
Citation - WoS: 29
Citation - Scopus: 32
Enhanced Hydrogen Storage of a Functional Material: Hf₂cf_{2< Mxene With Li Decoration}
(Elsevier, 2021) Gencer, Aysenur; Aydin, Sezgin; Surucu, Ozge; Wang, Xiaotian; Deligoz, Engin; Surucu, Gokhan
In this paper, the hydrogen storage properties of the Li-decorated stable Hf2CF2 MXene layer, obtained by the exfoliation of Al from Hf2AlC and F-termination, are considered by using first-principles calculations based on Density Functional Theory. First, the stability characteristics of the host structure (Hf2CF2 layer) are examined by investigating bulk Hf2AlC. To enhance the adsorbed number of H-2 molecules, the well-defined initial H-2 coordinates are constructed by CLICH (Cap-Like Initial Conditions for Hydrogens) and Monte Carlo-based algorithms. After the geometry optimizations of the designed H-2 systems on the Li/Hf2CF2 layer, the adsorption energies of nH(2)/Li/Hf2CF2 n = 1-10, 15, 20 and 25 systems are calculated, and the suitable values (0.2-0.6 eV/H-2) are obtained up to 15H(2). For n = 20 and 25 systems, which have adsorption energies of 0.15 eV/H-2 and 0.16 eV/H-2, respectively. The structural properties and adsorption geometries of these molecules are analyzed. Additionally, the partial density of the states, electron density difference maps, and Mulliken atomic charges are presented to identify the actual binding mechanism of the systems. The results reveal that the Li-decorated Hf2CF2 MXene layer can be preferred for the hydrogen storage applications due to its stable nature and the convenient adsorption characteristics.
Citation - WoS: 8
Citation - Scopus: 8
The Investigation of Electronic Nature and Mechanical Properties Under Spin Effects for New Half-Metallic Ferromagnetic Chalcogenides Ag₃crx_{4< (x = S, Se, and Te)}
(Elsevier, 2021) Erkisi, Aytac; Yildiz, Bugra; Wang, Xiaotian; Isik, Mehmet; Ozcan, Yusuf; Surucu, Gokhan
This study presents the electronic and mechanical characteristics of ternary silver-based Ag3CrX4 (X = S, Se, and Te) chalcogenides having simple cubic crystalline structure (SC), conforming P4-3m (space group: 215) that are studied under the spin-polarized Generalized Gradient Approach (GGA) within the framework of the Density Functional Theory (DFT). The stable magnetic phase has been determined as the ferromagnetic (FM) phase for all studied systems. Then, phase stability, mechanical, thermal and electronic characteristics of Ag3CrX4 chalcogenides have been reported. In the calculated spin polarized electronic band structures for Ag3CrX4 chalcogenides, as an indicator of half-metallic behavior, metallicity has been observed in the majority spin channel, while indirect band gaps (1.04 eV for Ag3CrS4, 1.10 eV for Ag3CrSe4, and 1.25 eV for Ag3CrTe4) have been determined in the minority spin channel. Moreover, Ag3CrX4 chalcogenides have been found as thermodynamically stable and structurally synthesizable considering the calculated negative formation enthalpies. Elastic constants of studied chalcogenides satisfying Born-Huang criteria's pointed out the mechanical stability of materials. The predicted mechanical properties determined with elastic constants revealed that Ag3CrX4 chalcogenides belong to soft and ductile material family.
Citation - WoS: 28
Citation - Scopus: 29
The investigation of electronic, anisotropic elastic and lattice dynamical properties of MAB phase nanolaminated ternary borides: M 2 AlB 2 ( M = Mn , Fe and Co ) under spin effects
(Elsevier Science Sa, 2020) Surucu, Gokhan; Yildiz, Bugra; Erkisi, Aytac; Wang, Xiaotian; Surucu, Ozge
[No Abstract Available]
Citation - WoS: 45
Citation - Scopus: 43
Investigation of Structural, Electronic, Magnetic and Lattice Dynamical Properties for Xcobi (x: Ti, Zr, Hf) Half-Heusler Compounds
(Elsevier, 2020) Surucu, Gokhan; Isik, Mehmet; Candan, Abdullah; Wang, Xiaotian; Gullu, Hasan Huseyin
Structural, electronic, magnetic, mechanical and lattice dynamical properties of XCoBi (X: Ti, Zr, Hf) Half-Heusler compounds have been investigated according to density functional theory and generalized gradient approximation. Among alpha, beta and gamma structural phases, gamma-phase structure has been found as the most stability characteristics depending on the calculated formation enthalpies, energy-volume dependencies and Cauchy pressures. Energy-volume plots of possible magnetic orders of gamma-phase XCoBi compounds have been analyzed and the most stable order has been found as paramagnetic nature. The theoretical studies on gamma-phase structures resulted in band gap energies of 0.96, 0.99 and 0.98 eV for TiCoBi, ZrCoBi and HfCoBi semiconducting compounds, respectively. Born-Huang criteria applied on elastic constants of interest compounds has indicated that gamma-phase is also mechanically stable for all studied compounds. In addition, various mechanical, lattice dynamical and thermodynamical parameters of XCoBi compounds have been calculated in the present study.
Citation - WoS: 48
Citation - Scopus: 49
Lattice Dynamical and Thermo-Elastic Properties of M₂alb (m = V, Nb, Ta) Max Phase Borides
(Elsevier Science Sa, 2020) Surucu, Gokhan; Gencer, Aysenur; Wang, Xiaotian; Surucu, Ozge
The structural, electronic, dynamic, and thermo-elastic properties of M2AlB (X = V, Nb, Ta) MAX phase borides were investigated using first principle calculations as implemented in the Vienna Ab-initio Simulation Package (VASP) with the generalized gradient approximation (GGA). The obtained structural properties and formation energies showed the thermodynamic stability and synthesizability of M2AlB. The electronic band structures were determined and they revealed that these compounds had a metallic character. The dynamic stability of M2AlB compounds were investigated with phonon dispersion curves and these compounds were found to be dynamically stable. The elastic constants were also calculated to determine the mechanical stability and to obtain the polycrystalline properties such as bulk modulus, shear modulus, etc. The thermo-elastic properties (thermal expansion coefficient, heat capacity, entropy, and free energy) were studied in a temperature range in between 0 and 1000 K and a pressure range in between 0 and 30 GPa. In addition, the direction dependent sound wave velocities were studied in three dimensions. Moreover, the minimum thermal conductivities and the diffusion thermal conductivities of these compounds were determined. This work is the processor study for the investigation of the main physical properties of M2AlB (M = V, Nb, Ta) ceramic compounds to date. (C) 2019 Elsevier B.V. All rights reserved.
Penta-Graphene/SnS2 Heterostructures with Z-Scheme Charge Transfer for Efficient Photocatalytic Water Splitting
(Amer Chemical Soc, 2025) Nasoz, Duygu Lale; Surucu, Ozge; Wang, Xiaotian; Surucu, Gokhan; Sarac, Yasemin; Gencer, Aysenur
The present study explores the photocatalytic potential of penta-graphene (PG) and SnS2 monolayers, along with their heterostructures (PG/SnS2), using Density Functional Theory (DFT). Structural analysis confirms that the PG/SnS2 heterostructure exhibits enhanced stability, efficient charge separation, and suitable band alignment. Optimized lattice parameters (3.66 & Aring; for PG and 3.88 & Aring; for SnS2) closely matched literature values, while ab initio molecular dynamics (AIMD) confirmed thermodynamic stability at 300 K. The heterostructure's band gap of 2.75 eV (HSE method) supports visible light absorption, and the band edge positions enable hydrogen and oxygen evolution reactions across pH 0 to 6. Optical analysis reveals significant visible-light absorption with an optical band gap of 1.43 eV. Additionally, this study identifies a Z-scheme charge transfer mechanism in the PG/SnS2 heterostructure, facilitated by an internal built-in electric field that drives directional charge migration, effectively enhancing electron-hole separation and suppressing recombination losses. This Z-scheme mechanism optimizes redox reactions, making PG/SnS2 a highly efficient photocatalyst for solar-driven hydrogen production. Furthermore, the effect of water solvent is investigated, and it reveals that this heterostructure is stable under water solvent, having suitable band edges for the photocatalytic water splitting. These findings highlight the PG/SnS2 heterostructure as a promising candidate for sustainable hydrogen generation, offering a new perspective for the design of next-generation 2D photocatalytic materials.