QR2-code

A DFT-based program for computation and analysis of the resonant Raman spectrum

The following papers that we have published describe the specific applications of QR2-code in several two-dimensional materials.

  1. Jianqi Huang, Renhui Liu, Ye Zhang et al, QR2-code: An open-source program for double resonance Raman spectra, arXiv:2505.10041 (2025)

    2. We present an open-source program QR2-code that computes double-resonance Raman (DRR) spectra using first-principles calculations. QR2-code can calculate not only two-phonon DRR spectra but also single-resonance Raman spectra and defect-induced DRR spectra. For defect-induced DDR spectra, we simply assume that the electron-defect matrix element of elastic scattering is a constant. Hands-on tutorials for graphene are given to show how to run QR2-code for single-resonance, double-resonance, and defect-induced Raman spectra. We also compare the single-resonance Raman spectra by QR2-code with that by QERaman code. In QR2-code, the Raman spectrum is calculated by the time-dependent perturbation theory, in which the energy dispersions of electron and phonon are taken from Quantum ESPRESSO (QE) code and the electron-phonon matrix element is obtained from the modified Electron-Phonon-Wannier (EPW) code. All codes, examples, and scripts are available on the GitHub repository.

  2. Jianqi Huang, Huaihong Guo, Lin Zhou et al, First-principles calculations of double resonance Raman spectra for monolayer MoTe2, Physical Review B 105, 235401 (2022)

    3. In this paper, we calculate the double resonant Raman (DRR) spectrum of monolayer MoTe2. Furthermore, we perform an analysis of the possible DRR modes over the Brillouin zone, highlighting the role of low-symmetry points. Raman tensors for some DRR modes are given by first-principles calculations from which laser polarization dependence is obtained.

  3. Shishu Zhang, Jianqi Huang, Yue Yu et al, Quantum interference directed chiral raman scattering in two-dimensional enantiomers, Nature Communications 13, 1254 (2022)

    4. The elementary Raman processes via all possible pathways can interfere with each other, giving rise to intriguing scattering effects. Here we report that quantum interference can lead to significant chiral Raman response in monolayer transitional metal dichalcogenide with triclinic symmetry. Large circular intensity difference observed for monolayer rhenium dichalcogenide originates from inter-k interference of Raman scattering excited by circularly polarized light with opposite helicities. Our results reveal chiral Raman spectra as a new manifestation of quantum interference in Raman scattering process.

  4. Jianqi Huang, Zhiyong Liu, Teng Yang et al, New selection rule of resonant Raman scattering in MoS2 monolayer under circular polarization, Journal of Materials Science & Technology 102 (2022) 132–136

    5. The first-order resonant Raman spectra of monolayer MoS2 are calculated under the circularly polarized photoexcitation. The anomalously nonzero Raman intensity of the in-plane E mode under the -Z(σ+σ+)Z or -Z(σ-σ-)Z geometry, which goes against the conventional selection rule, appears under some circumstances when optical absorption occurs at some special reciprocal points between the zone-center and the zone-edge-center M points.

  5. Yujia Pang, Jianqi Huang, Teng Yang et al, Accurate assignment of double resonant Raman bands in Janus MoSSe monolayer from first-principles calculations, Journal of Materials Science & Technology 131 (2022) 82–90

    6. In this work, we calculate the double resonant Raman (DRR) spectra of Janus MoSSe monolayer within the first-principles framework and succeed in achieving accurate assignments of the DRR bands. The assignments are in agreement with our group theoretical analysis. Moreover, taking advantage of its strain-sensitive feature, we calculate the DRR spectra under biaxial strain, and further verify the rationality of our assignments by analyzing strain-induced shift of the DRR bands.

  6. Renhui Liu, Jianqi Huang, Teng Yang et al, Helicity selection rule of double resonance Raman spectra for monolayer MoSe2, Physical Review B 110, 245422 (2024)

    7. Helicity selection rule of single-resonance Raman spectra of TMDCs is rather interesting, but helicity selection rule of double-resonance Raman spectra of TMDCs remains elusive. In this paper, we study second-order Raman spectra of monolayer MoSe2 by using circularly polarized light at four laser energies resonant with the C exciton. From both experiment and calculation, helicity-dependent Raman spectra show that the overtone mode of a helicity-changing mode observed at 560–610 cm-1 is a helicity-conserved mode, while the combinational mode of helicity-changing modes is still a helicity-changing mode. We discuss the selection rule of helicity-dependent double resonance Raman spectra by using first-principles density functional calculations and Raman tensor analysis, in which overtone and combinational modes give exactly opposite helicity-dependent behaviors after the decomposition to the \(\Gamma\) point.

  7. Ye Zhang, Renhui Liu, Jianqi Huang, Teng Yang et al, DUV Double-Resonant Raman Spectra and Interference Effect in Graphene: First-Principles Calculations, Journal of Raman Spectroscopy 56, 316–323 (2025)

    8. In this paper, we calculate double-resonance Raman (DRR) spectra of monolayer graphene by using the QR2-code, for wide laser excitation energies from the near-infrared (1.58 eV) to the deep-ultraviolet (DUV, 5.41 eV) region. Rich properties are unveiled including laser energy dependence of Raman intensity in G' (2D), 2D' and G* bands. Further, the DRR scattering processes of G′ band are exploited in the perspective of the quantum interference effect between four scattering processes (electron-hole (eh), he, ee, hh). The calculated Raman spectra are directly compared and consistent with the experimental results.

  8. Weidong Wang, Renhui Liu, Huaihong Guo, Jianqi Huang, Teng Yang et al, Anomalous lattice vibration in monolayer MoS2 induced by DUV laser: A first-principles investigation, Chinese Physics B 34, 066301 (2025)

    9. Deep-ultraviolet (DUV) laser-induced anomalous lattice dynamics in MoS2 monolayer is experimentally observed by Raman spectroscopy and explained by calculations using the QR2-code. Our calculations reveal that the DUV laser-induced anomalous lattice dynamics stems from the quantum interference effect among different Raman scattering channels.

  9. Riichiro Saito, Nguyen Tuan Hung, Teng Yang, Jianqi Huang et al, Deep Ultraviolet and Helicity Dependent Raman Spectroscopy for Carbon Nanotubes and 2D Materials, Small 202308558 (2024)

    10. Recent progress of Raman spectroscopy on carbon nanotubes and 2D materials is reviewed as a topical review.