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Article Citation - WoS: 8Citation - Scopus: 8Complex 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, XiaotianTopological 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.Article Citation - WoS: 1Citation - Scopus: 1Penta-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, AysenurThe 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.
