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Symmetry (physics)

About: Symmetry (physics) is a research topic. Over the lifetime, 26435 publications have been published within this topic receiving 500189 citations. The topic is also known as: symmetry (physics) & physical symmetry.


Papers
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Journal ArticleDOI
TL;DR: The symmetry properties of molecular orbitals and of reaction coordinates can be used to decide on the feasibility of selected chemical reaction mechanisms as discussed by the authors, where reaction paths are shown to have a large energy barrier and are said to be "forbidden by orbital symmetry".
Abstract: The symmetry properties of molecular orbitals and of reaction coordinates can be used to decide on the feasibility of selected chemical reaction mechanisms. Some reaction paths are shown to have a large energy barrier and are said to be “forbidden by orbital symmetry.” The reactions of molecules with no symmetry can also be analyzed by being compared to related symmetric molecules, where the molecular orbitals are topological identical.

118 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a new methodology for constructing feedback control laws for a symmetric spacecraft with two control torques supplied by gas jet actuators, based on a new formulation for the attitude kinematics.

118 citations

Journal ArticleDOI
TL;DR: The basic equations relating the five independent second-order elastic stiffness constants (fourth-rank tensor) to the ultrasonic wave speeds in a hexagonal medium are derived, with special emphasis on determining the microtextural symmetry of human cortical bone.

118 citations

Journal ArticleDOI
TL;DR: A spin-adapted density matrix renormalization group (DMRG) algorithm designed to target spin and spatial symmetry states that can be difficult to obtain while using a non-spin- Adapted algorithm is presented.
Abstract: We present a spin-adapted density matrix renormalization group (DMRG) algorithm designed to target spin and spatial symmetry states that can be difficult to obtain while using a non-spin-adapted algorithm. The algorithmic modifications that have to be introduced into the usual density matrix renormalization group scheme in order to spin adapt it are discussed, and it is demonstrated that the introduced modifications do not change the overall scaling of the method. The new approach is tested on HNCO, a model system, that has a singlet-triplet curve crossing between states of the same symmetry. The advantages of the spin-adapted DMRG scheme are discussed, and it is concluded that the spin-adapted DMRG method converges better in almost all cases and gives more parallel curves to the full configuration interaction result than the non-spin-adapted method. It is shown that the spin-adapted DMRG energies can be lower than the ones obtained from the non-spin-adapted scheme. Such a counterintuitive result is explained by noting that the spin-adapted method is not a special case of the non-spin-adapted one; consequently, the spin-adapted result is not an upper bound for the non-spin-adapted energy.

118 citations

Journal Article
TL;DR: In this paper, a thorough group theory study of the symmetry aspects relevant to optical and spectroscopic analysis, for the most common polytypes of transition metal dichalcogenides, i.e., 2 Ha, 2 Hc and 1T, is presented.
Abstract: Transition metal dichalcogenides (TMDCs) have emerged as a new two-dimensional material’s field since the monolayer and few-layer limits show different properties when compared to each other and to their respective bulk materials. For example, in some cases when the bulk material is exfoliated down to a monolayer, an indirect-to-direct band gap in the visible range is observed. The number of layers N (N even or odd) drives changes in space-group symmetry that are reflected in the optical properties. The understanding of the space-group symmetry as a function of the number of layers is therefore important for the correct interpretation of the experimental data. Here we present a thorough group theory study of the symmetry aspects relevant to optical and spectroscopic analysis, for the most common polytypes of TMDCs, i.e., 2 Ha ,2 Hc and 1T ,a s af unction of the number of layers. Real space symmetries, the group of the wave vectors, the relevance of inversion symmetry, irreducible representations of the vibrational modes, optical activity, and Raman tensors are discussed.

118 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202217
20211,679
20201,178
20191,006
20181,040
2017939