Mechanism of negative thermal expansion in LaC2 from first-principles prediction

Liu, Yaming; Jia, Yu; Sun, Qiang; Liang, Erjun

doi:10.1016/j.physleta.2014.10.041

Cited by 10 publications

(6 citation statements)

References 31 publications

(39 reference statements)

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“…can be calculated from the phonon density of states (DOS) as a function of frequencies, which were carried out in the framework of quasiharmonic approximation (QHA). In our previous works [24][25][26], this method provided reasonable and intriguing description of the dynamic properties of materials below the melting point.…”

Section: Methodsmentioning

confidence: 93%

Negative thermal expansion in isostructural cubic ReO 3 and ScF 3 : A comparative study

Liu

Wang

et al. 2015

Computational Materials Science

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Section: Methodsmentioning

confidence: 93%

Negative thermal expansion in isostructural cubic ReO 3 and ScF 3 : A comparative study

Liu

Wang

et al. 2015

Computational Materials Science

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“…The three acoustic phonon branches include the in-plane longitudinal acoustic (LA), transverse acoustic (TA), and out-of-plane transverse acoustic (ZA) modes, with the ZA mode having a quadratic relation at the point while the other two have linear relations. The optical phonon branches contain in-plane and longitudinal out-of-plane transverse optical modes with symmetric and antisymmetric vibrational orientations. , …”

Section: Resultsmentioning

confidence: 99%

“…The optical phonon branches contain inplane and longitudinal out-of-plane transverse optical modes with symmetric and antisymmetric vibrational orientations. 73,74 The phonon spectra of the β-CuSCN are divided into four regions: two low-frequency regions (below 9 THZ), one 74 It can be attributed to sizable atomic mass, which decreases phonon frequency as the same as seen for MX 2 (M = Mo, W; X = S, Se, Te). 75 Even though the highest phonon frequencies are presented, the phonon modes below 25 THz are substantially suppressed, and the frequency gap disappears.…”

Section: Computational Detailsmentioning

confidence: 99%

DFT Computational Approach to Interfacial Recombination in MXene-Assisted Perovskite Solar Cells with β-CuSCN HTL

Asgharizadeh,

Azadi,

Zeynali

2023

J. Phys. Chem. C

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A new class of two-dimensional (2D) metal carbides, nitrides, and carbonitrides called MXenes has gathered more interest due to their photovoltaic applications. For the MXenes, different surface termination techniques grant them various roles to improve the perovskite solar cell (PSC) performance. Based on the experimental evidence, the bandgap of the active layers in the PSC was not altered; however, their work function was greatly influenced. We report the influence of additive Ti 3 C 2 T x MXene into the absorber and electron transport layers in a PSC, and how it is beneficial to boost the PSC performance using the Solar Cell Capacitance Simulator (SCAPS) simulation tool. The considered architecture contains the methylammonium lead triiodide (MAPbI 3 ) absorber layer, TiO 2 electron transport layer, and CuSCN hole transport layer (HTL). The first-principles density functional theory (DFT) calculations were utilized to get the optical and electrical properties of the β-CuSCN HTL. An optimization procedure was taken to improve the power conversion efficiency (PCE). An overall conversion efficiency of 22.73% can be achieved with MXene assisted structure which is mainly due to a reduction in conduction and valence band offsets that have occurred through the adjustment of electron affinity in the absorber and electron transport layers.

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“…In the high-frequency region, it is caused by the stretching vibration of the C≡N triplet bond. These phonon frequency regions can be well explained by the structure and chemical bonds of the system (Liu et al, 2015). According to previous studies (Dove and Fang, 2016;Mittal et al, 2018;Gao et al, 2020b), we know that phonons in the low-frequency region have a great influence on the thermal expansion characteristics at low temperatures.…”

Section: Phonon Dispersion and Grüneisen Parametersmentioning

confidence: 85%

“…Detailed discussion of the QHA can be found in the references (Kuzkin and Krivtsov, 2015). In our previous work, the QHA provided a reasonable description of the dynamic properties of the compound (Liu et al, 2015;Chang et al, 2018;Li et al, 2020).…”

Section: Computation Methodsmentioning

confidence: 97%

Theoretical Study of Abnormal Thermal Expansion of CuSCN and Effect on Electronic Structure

et al. 2021

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CuSCN, as a new type of inorganic hole-transporting semiconductor with a wide bandgap (>3.4 eV), is attracting much attention in the fabrication of perovskite solar cells. In this article, by using first-principles density functional theory (DFT) and the quasi-harmonic approximation (QHA) approach, we have studied lattice dynamics and abnormal thermal expansion of the system, including α- and β-CuSCN phases. The influence of the abnormal thermal expansion of the lattice on the electronic structure, especially on the bandgap of the system, was explored and discussed. We found that due to the shearing modes and the three acoustic modes along the direction of the c-axis, the α- and β-CuSCN show a negative thermal expansion (NTE) in the direction of the c-axis. The torsion modes of the Cu–N–C–S atomic chains in the α-CuSCN may lead to an NTE in the directions of the a, b-axes of the α-phase. As a result, our theoretical results demonstrated that the α-CuSCN exhibits an anisotropic bulk NTE. While the β-CuSCN displays a strong uniaxial negative thermal expansion in the direction of the c-axis, in the directions of the a, b-axes, it exhibits positive thermal expansion. Our DFT calculations also predicted that the α-CuSCN has a direct bandgap, which increases slightly with increasing temperature. However, the β-CuSCN has an indirect bandgap at low temperature, which converts to a direct bandgap near the temperature of 375 K due to the strong positive expansion in the ab plane of the phase. Our work revealed the mechanisms of the abnormal thermal expansion of the two phases and a strong coupling between the anisotropic thermal expansion and the electronic structures of the system.

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Mechanism of negative thermal expansion in LaC2 from first-principles prediction

Cited by 10 publications

References 31 publications

Negative thermal expansion in isostructural cubic ReO 3 and ScF 3 : A comparative study

Negative thermal expansion in isostructural cubic ReO 3 and ScF 3 : A comparative study

DFT Computational Approach to Interfacial Recombination in MXene-Assisted Perovskite Solar Cells with β-CuSCN HTL

Theoretical Study of Abnormal Thermal Expansion of CuSCN and Effect on Electronic Structure

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