Quantum Unfolding: A program for unfolding electronic energy bands of materials

Abstract

a b s t r a c tWe present Quantum Unfolding, a Fortran90 program for unfolding first-principles electronic energy bands. It unfolds energy bands accurately by handling the Fourier components of Bloch wavefunctions, which are reconstructed from Wannier functions from Wannier90. Due to the wide application of Wannier90 package and the possibility of focusing only on the most important energy bands, the present code works very conveniently. Program summary Program title: Quantum Unfolding Catalogue identifier: AEVF_v1_0Program summary URL: Cat IdTitle Reference AEAK_v2_0 wannier90 CPC 185 (2014)2309Nature of problem:The Brillouin zone of a supercell is smaller than that of a primary cell. It makes the supercell energy bands more crowded. The crowded energy bands are outright difficult, if not impossible, to be compared with experimental results directly. Besides, the intra-supercell translation symmetries are hidden in the supercell band structure calculations. In order to compare with experiments and catch the hidden symmetries, we have to unfold the supercell energy bands into the corresponding primary-cell Brillouin zone. Solution method:The electron wavefunction is reconstructed from Wannier functions and Hamiltonian parameters, which are produced by Wannier90 package. Then by using fast Fourier transformation (FFT), we get the Fourier components of the reconstructed wavefunction. The unfolding weight is calculated from the Fourier components, based on group theory and its special form for plane-wave basis. Unusual features:Simple and user-friendly input system. Great efficiency and high unfolding speed. Running time:System dependent, from a few minutes to several hours.

Ordered and Disordered Phases in Mo1−xWxS2 Monolayer

“…The lattice vectors and atom coordinates are fully relaxed until the forces are below 0.01 eV/Å. We use quantum unfolding (QU) method to unfold the band structure of alloy from supercell method into the fist Brillouin zone of primitive cell with QU band unfolding code 45 , 46 .…”

Evidence of Large Polarons in Photoemission Band Mapping of the Perovskite Semiconductor CsPbBr3

“…However, the spectral weight transfer to the novel bands is proportional to the strength of the perturbing potential and often hardly observable [61], e.g., for the methylammonium lead triiodide perovskite (MAPbI 3 ) [62,63], where no signatures of backfolded orthorhombic bands were observed by ARPES, despite a clear orthorhombic diffraction pattern. To calculate explicitly the spectral weight transfer upon the structural distortions, we follow a band unfolding procedure proposed by Ku et al [64] and implemented in the Quantum ESPRESSO package [65]. The calculations confirm the absence of significant spectral weight transfer to the backfolded upper valence band in the orthorhombic phase [30].…”

Understanding the Band Engineering in Mg2Si‐Based Systems from Wannier‐Orbital Analysis

“…In order to better visualize the band convergence effect, the energy bands of the supercell were unfolded into the corresponding unitcell IBZ by the quantum unfolding method to calculated the unfolding weight. [33]…”