化学
结晶学
电负性
核磁共振谱数据库
带隙
固态核磁共振
化学位移
耦合
谱线
电子结构
核磁共振波谱
核磁共振
凝聚态物理
计算化学
立体化学
物理化学
物理
有机化学
天文
作者
Amit Bhattacharya,Vidyanshu Mishra,Dylan Tkachuk,Arthur Mar,Vladimir K. Michaelis
摘要
Chalcogenides are an important class of materials that exhibit tailorable optoelectronic properties accessible through chemical modification. For example, the minerals kesterite, stannite, and velikite (Cu2MSnS4, where M = Zn, Cd, or Hg, respectively) are a series of Group 12 transition metal tin sulfides that readily exhibit optical bandgaps spanning the Shockley-Queisser limit; however, achieving consensus on their structure (space group I4̄ vs. I4̄2m) has been difficult. This study explores the average long-range and local structure of Cu2HgSnS4 and evaluates the parallels of M = Zn and Cd sister compounds using complementary X-ray diffraction and solid-state nuclear magnetic resonance (NMR) spectroscopy. The 63/65Cu NMR spectra were acquired at multiple magnetic field strengths (B0 = 7.05, 11.75, and 21.1 T) to assess the unique chemical shift anisotropy and quadrupolar coupling contributions. They reveal two inequivalent sets of Cu sites in Cu2ZnSnS4, in contrast to only one set of sites in Cu2CdSnS4 and Cu2HgSnS4, clarifying structural assignments previously proposed through X-ray diffraction methods. The presence of these Cu sites was further supported by DFT calculations. The 119Sn and 199Hg NMR spectra suggest that an ordering phenomenon takes place in Cu2HgSnS4 when it undergoes annealing treatments. The trend in measured optical band gaps (1.5 eV for Cu2ZnSnS4, 1.2 eV for Cu2CdSnS4, and 0.9 eV for Cu2HgSnS4) was confirmed by electronic structure calculations, which show that the band gap narrows as the difference in electronegativity is diminished and that Hg-S bonds in Cu2HgSnS4 have greater covalent character.
科研通智能强力驱动
Strongly Powered by AbleSci AI