<i>Ab initio</i>
 evidence for nonthermal characteristics in ultrafast laser melting

Lian, Chao; Zhang, S. B.; Meng, Sheng

doi:10.1103/physrevb.94.184310

Cited by 40 publications

(40 citation statements)

References 48 publications

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“…A larger value corresponds to more order (centrosymmetry), but note the inverted axis. [13]. The nonlinearity of the RMSD in the initial ∼150 fs after the excitation indicates that a small activation barrier to melting remains, in general agreement with Refs.…”

Section: Discussionsupporting

confidence: 76%

“…2(b) along with the experimental measurements (circle). Also shown is the (220) peak decay computed with real-time time-dependent DFT by Lian et al [13] for the same level of excitation. The peak rapidly decays within a picosecond in all cases, although the simulations both predict a quicker collapse of the structure than the experimental data would imply.…”

Section: Discussionmentioning

confidence: 99%

“…(b) The normalized response of the (220) Bragg peak to a high-fluence laser pulse that nonthermally melts the crystal. The ab initio data (dashed line) was taken from [13] and the experimental data (circles) from Ref. [2].…”

Section: Discussionmentioning

confidence: 99%

“…These studies do predict bond softening at high excitations but they predict melting to occur at higher excitations than expected based on experiment. More recent methods [13,14] have avoided these two assumptions and, consequently, predicted melting at lower excitations. However, it is unclear to what ex-tent this is attributable to the more realistic electronic distributions versus the nonadiabatic effects.…”

Section: Introductionmentioning

confidence: 99%

“…Silicon is a widely studied material in the context of strongly driven phase transitions, both experimentally [1][2][3][4][5][6] and theoretically [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29], where it is found to melt on a subpicosecond timescale at high excitations. Most theoretical studies of nonthermal melting in silicon have employed ab initio simulation methods.…”

Section: Introductionmentioning

confidence: 99%

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Simulating electronically driven structural changes in silicon with two-temperature molecular dynamics

Darkins

Murphy

et al. 2018

Phys. Rev. B

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Radiation can drive the electrons in a material out of thermal equilibrium with the nuclei, producing hot, transient electronic states that modify the interatomic potential energy surface. We present a rigorous formulation of two-temperature molecular dynamics that can accommodate these electronic effects in the form of electronic-temperature-dependent force fields. Such a force field is presented for silicon, which has been constructed to reproduce the ab initio-derived thermodynamics of the diamond phase for electronic temperatures up to 2.5 eV, as well as the structural dynamics observed experimentally under nonequilibrium conditions in the femtosecond regime. This includes nonthermal melting on a subpicosecond timescale to a liquidlike state for electronic temperatures above ∼1 eV. The methods presented in this paper lay a rigorous foundation for the large-scale atomistic modeling of electronically driven structural dynamics with potential applications spanning the entire domain of radiation damage.

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Section: Discussionsupporting

confidence: 76%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Simulating electronically driven structural changes in silicon with two-temperature molecular dynamics

Darkins

Murphy

et al. 2018

Phys. Rev. B

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Photoexcitation in Solids: First‐Principles Quantum Simulations by Real‐Time TDDFT

Lian

Guan

et al. 2018

Advcd Theory and Sims

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An efficient and state-of-the-art real-time time-dependent density functional theory (rt-TDDFT) method is presented, as implemented in the time-dependent ab initio package (TDAP), which aims at performing accurate simulations of the interaction between laser fields and solid-state materials. The combination of length-gauge and velocity-gauge electromagnetic field has extended the diversity of materials under consideration, ranging from low dimensional systems to periodic solids. Meanwhile, by employing a local basis presentation, systems of a large size are simulated for long electronic propagation time, with moderate computational cost while maintaining a relatively high accuracy. Non-perturbative phenomena in materials under a strong laser field and linear responses in a weak field can be simulated, either in the presence of ionic motions or not. Several quintessential works are introduced as examples for applications of this approach, including photoabsorption properties of armchair graphene nanoribbon, hole-transfer ultrafast dynamics between MoS 2 /WS 2 interlayer heterojunction, laser-induced nonthermal melting of silicon, and high harmonic generation in monolayer MoS 2 . The method demonstrates great potential for studying ultrafast electron-nuclear dynamics and nonequilibrium phenomena in a wide range of quantum systems.ultrafast dynamics and phenomena either in perturbative or non-perturbative regimes. [3][4][5][6][7][8] Therefore, it has been a unique ab initio quantum method applicable for the exploring of strong field physics beyond linear response theory, for instance, high harmonic generation [9,10] and ultrafast photoelectron emission. [11] Recently, the scope of rt-TDDFT applications has greatly extended from treating isolated atomic and molecular systems to condensed phase materials. In most previous works, numerical implementations of rt-TDDFT that aim at handling solid materials were built on real-space grids, [12,13] including some well-known program packages such as OCTOPUS [9,14] and SALMON. [15,16] Real-time TDDFT has also been implemented in plane wave codes, for example, the ELK FP-LAPW [17] and FPSID, [18] whose encouraging results have shown the effectiveness of the rt-TDDFT approaches. However, if one is interested in high energy excitation that is on the energy scale of tens to hundreds of electron volts (eV), extremely dense real-space grids and high kinetic energy of plane waves are indispensable. Meanwhile, to describe a system with N a atoms, 10 3 to 10 4 × N a real-space grids or plane waves have to be used, which makes the simulation of large-size systems impractical using computer resources available at the present stage. The above two factors will significantly increase the computational cost and in turn limit the practicability of the rt-TDDFT methods.Here we introduce a real-time ab initio approach based on local atomic basis for simulating electron-nuclear dynamics under laser excited conditions. This approach has been successfully implemented in the time-dependent ab initi...

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Photoexcited charge carrier behaviors in solar energy conversion systems from theoretical simulations

Wei

Huang

Dai

2019

WIREs Comput Mol Sci

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Solar energy bears great potential in the substitution of conventional fossil fuels to enable a sustainable world. In order to harness and use solar energy, photocatalytic and photovoltaic systems made of semiconductor materials have been developed to convert sunlight into energy (electricity) based on the photoelectrochemical effects.Photoelectric events are related with the light-energy (electricity) conversion process, including photon absorption, photoexcited charge carrier separation and recombination, charge carrier transport, and photocurrent generation, as well as electron plasmonic resonance. We focus on the recent state-of-the-art simulation methods correspondingly mimicking these photogenerated charge carrier behaviors, taking electron-phonon, electron-exciton, and exciton-exciton interactions into account. Results can be obtained from the standard density function theory (DFT) for ground-state properties, many-body perturbation theory for band gap renormalization and optical absorption, time-domain DFT in combination with nonadiabatic molecular dynamics for photoexcitation dynamics, nonequilibrium Green's function and self-consistent theory for charge carrier transport properties, and classical Maxwell's equations in discrete dipole approximation for localized surface plasmon resonance absorption and near-field enhancement. In combination of the results from these simulation methods, a complete and consistent picture describing the fundamental photoelectric process in light-energy (electricity) conversion could be obtained. Simulation results offer guidelines for experimental efforts and provide new basic insights into the underlying mechanisms and the design principles for next-generation photocatalytic and photovoltaic devices of high solar light utilization efficiency.

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Ab initio evidence for nonthermal characteristics in ultrafast laser melting

Cited by 40 publications

References 48 publications

Simulating electronically driven structural changes in silicon with two-temperature molecular dynamics

Simulating electronically driven structural changes in silicon with two-temperature molecular dynamics

Photoexcitation in Solids: First‐Principles Quantum Simulations by Real‐Time TDDFT

Photoexcited charge carrier behaviors in solar energy conversion systems from theoretical simulations

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