Search

Decreasing of layer thickness causes the decrease of polarization until it disappears due to the existence of depolarization field. Therefore, the search for strong piezoelectric materials is highly desirable for multifunctional ultra-thin piezoelectric devices. Herein, we propose a common strategy for achieving strong piezoelectric materials through the electronic asymmetry induced by the intrinsically asymmetric atomic character of different chalcogen atoms. Accordingly, in the tetrahedral lattice structures, for example, M4X3Y3 (M = Pd/Ni, X/Y = S, Se or Te, X ≠ Y) monolayers are proved to display excellent out-of-plane piezoelectricity. Ni4Se3Te3 possesses the largest piezoelectric coefficient d33 of 61.57 pm/V, which is much larger than that of most 2D materials. Enhancing the electronic asymmetry further increases the out-of-plane piezoelectricity of Janus M4X3Y3 materials. Correspondingly, the out-of-plane piezoelectricity is positively correlated with the ratio of electronegativity difference (Red) and the electric dipole moment (P). This work provides alternative materials for energy harvesting nano-devices or self-energized wearable devices, and supplies a valuable guideline for predicting 2D materials with strong out-of-plane piezoelectricity. [ABSTRACT FROM AUTHOR]

In the search for clues to the matter–antimatter puzzle, experiments with atoms or molecules play a particular role. These systems allow measurements with very high precision, as demonstrated by the unprecedented limits down to 10−30 e cm on electron EDM using molecular ions, and relative measurements at the level of 10−12 in spectroscopy of antihydrogen atoms. Building on these impressive measurements, new experimental directions offer potential for drastic improvements. We review here some of the new perspectives in those fields and their associated prospects for new physics searches. This article is part of the theme issue 'The particle-gravity frontier'. [ABSTRACT FROM AUTHOR]

Detecting a non-zero electric dipole moment in a particle would unambiguously signify physics beyond the Standard Model. A potential pathway towards this is the detection of a nuclear Schiff moment, the magnitude of which is enhanced by the presence of nuclear octupole deformation. However, due to the low production rate of isotopes featuring such 'pear-shaped' nuclei, capturing, detecting and manipulating them efficiently is a crucial prerequisite. Incorporating them into synthetic diamond optical crystals can produce defects with defined, molecule-like structures and isolated electronic states within the diamond band gap, increasing capture efficiency, enabling repeated probing of even a single atom and producing narrow optical linewidths. In this study, we used density functional theory to investigate the formation, structure and electronic properties of crystal defects in diamond containing 229Pa , a rare isotope that is predicted to have an exceptionally strong nuclear octupole deformation. In addition, we identified and studied stable lanthanide-containing defects with similar electronic structures as non-radioactive proxies to aid in experimental methods. Our findings hold promise for the existence of such defects and can contribute to the development of a quantum information processing-inspired toolbox of techniques for studying rare isotopes. This article is part of the Theo Murphy meeting issue 'Diamond for quantum applications'. [ABSTRACT FROM AUTHOR]

Atomic partial charges cannot be physically measured but they play a significant role in many chemical theories and theoretical models. Therefore, they are, evaluated from experimentally acquired properties or calculated by quantum chemistry computational methods. This study is focused on determining chemical accuracy of various theoretical methods of computing atomic partial charges based on quantum chemistry. Values of gas-phase atomic partial charges were acquired by Mulliken (MUL) population analysis, natural bond analysis (NBO), Merz-Singh-Kollman (MSK) scheme, and atomic polar tensor (APT) charges computed considering Density Functional Theory and ab initio Møller-Plesset up to the second order levels. Correlations between the calculated values were determined by principal component analysis (PCA) and further confirmed by linear regression. The best agreement between experimentally evaluated atomic partial charges and theoretical values was obtained with the MSK scheme. [ABSTRACT FROM AUTHOR]