Exploring the deep interior of ice giants with shock-compression experiments and ab initio simulations: The case of metallic ammonia 

Author(s):  
Mandy Bethkenhagen ◽  
Jean-Alexis Hernandez ◽  
Alessandra Benuzzi-Mounaix ◽  
Frederic Datchi ◽  
Martin French ◽  
...  

<p>Ammonia is predicted to be one of the major components in the depths of the ice giant planets Uranus and Neptune. Their dynamics, evolution, and interior structure are insufficiently understood and models rely imperatively on data for equation of state and transport properties [1,2]. Despite its great significance, the experimentally accessed region of the ammonia phase diagram today is still very limited in pressure and temperature [3, 4].</p><p>We investigate the equation of state, the optical properties and the electrical conductivity of warm dense ammonia by combining laser-driven shock experiments and state-of-the-art density functional theory molecular dynamics (DFT-MD) simulations [5]. The equation of state is probed along the Hugoniot of liquid NH<sub>3 </sub>up to 350 GPa and 40000 K and in very good agreement with earlier DFT-MD results [6]. Our temperature measurements show a subtle slope change at 7000 K and 90 GPa, which coincides with the gradual transition from a liquid dominated by molecules to a plasma state in our new ab initio simulations. The reflectivity data furnish the first experimental evidence of electronic conduction in high pressure ammonia and are in excellent agreement with the reflectivity computed from atomistic simulations. Corresponding electrical conductivity values are found up to one order of magnitude higher than in water in the 100 GPa regime, with possible implications on the generation of magnetic dynamos in large icy planets’ interiors.</p><p> </p><p>[1] Scheibe, Nettelmann, Redmer, Astronomy & Astrophysics <strong>632</strong>, A70 (2019).</p><p>[2] Vazan & Helled, Astronomy & Astrophysics <strong>633</strong>, A50 (2020).</p><p>[3] Nellis, Hamilton, Holmes, Radousky, Ree, Mitchell, Nicol, Science <strong>240</strong>, 779 (1988).</p><p>[4] Radousky, Mitchell, Nellis, Journal of Chemical Physics <strong>93</strong>, 8235 (1990).</p><p>[5] Ravasio, Bethkenhagen, Hernandez, Benuzzi-Mounaix, Datchi, French, Guarguaglini, Lefevre, Ninet, Redmer, Vinci, Physical Review Letters <strong>126</strong>, 025003 (2021).</p><p>[6] Bethkenhagen, French, Redmer, Journal of Chemical Physics <strong>138</strong>, 234504 (2013).</p>

Author(s):  
Nguyen Huu Tho ◽  
Trang Thanh Tu ◽  
Trac Minh Nhan ◽  
Pham Hong Cam ◽  
Pham Thi Thi

The geometries, stabilities of VGen0/- (n = 9 - 13) clusters were systematically studied by the density functional theory (DFT) using the BP86 functional and LANL2DZ basis set. Several possible multiplicities of each cluster were tested to determine the most stable structure among the isomers. The average binding energy per atom, fragmentation energy, second order energy difference and HOMO-LUMO gaps were evaluated. The results indicated that the neutral and anionic clusters possess higher stability when n = 10 and 12. The vertical detachment energy (VDE) and adiabatic detachment energy (ADE) were also calculated for anionic cluster to investigate their stabilities. Among neutral clusters, VGe10 had both the highest vertical ionization potential (VIP) and chemical hardness. Keywords BP86/LANL2DZ, binding energy, VGen0/- clusters, structure of clusters References [1] Shunping Shi, Yiliang Liu, Chuanyu Zhang, Banglin Deng, Gang Jiang (2015). A Computational Investigation of Aluminum-doped Germanium Clusters by Density Functional Theory Study. Computational and Theoretical Chemistry, 1054, pp. 8-15[2] Wen-Jie Zhao, Yuan-Xu Wang (2009). Geometries, stabilities, and Magnetic Properties of MnGen (n = 2 – 16) Clusters: Density-functional Theory Investigations. Journal of Molecular Structure: THEOCHEM, 901 (1–3), pp. 18-23.[3] Shi Shun-Ping, Liu Yi-Liang, Deng Bang-Lin, Zhang Chuan-Yu, and Jiang Gang (2016). Density Functional Theory Study of The Geometrical and Electronic Structures of (n = 1 - 9) clusters. World Scientific Publishing Company, 30, pp. 1750022-1750039.[4] J.Stato, H.Kobayashi, K. Ikarashi, N.Saito, H.Nishiyama, and Y. Inoue (2004). Photocatalitic Activity for Water Decomposition of RuO2-Dispersed Zn2GeO4 with d10 Configuration. The Journal of Physical Chemistry B, 108 (14), pp. 4369-4375.[5] Daoxin Dai, Molly Piels, and John E. Bowers (2014). Monolithic Germanium/Silicon Photodetectors With Decoupled Structures: Resonant APDs and UTC Photodiodes. IEEE Journal of Selected Topics in Quantum Electronics, 20 (6), pp. 3802214-3802227.[6] Chia-Yun Chou, Gyeong S. Hwang (2014). On The Origin of The Significant Difference in Lithiation Behavior Between Silicon and Germanium. Journal of Power Sources, 263, pp. 252-258.[7] Siwen Zhang, Bosi Yin, Yang Jiao, Yang Liu, Xu Zhang, Fengyu Qu, Ahmad Umar, Xiang Wu (2014). Ultra-long Germanium Oxide Nanowires: Structures and Optical Properties. Journal of Alloys and Compounds, 606, pp. 149-153.[8] T. Herrmannsdörfer, V. Heera, O. Ignatchik, M. Uhlarz, A. Mücklich, M. Posselt, H. Reuther, B. Schmidt, K.-H. Heinig, W. Skorupa, M. Voelskow, C. Wündisch, R. Skrotzki, M. Helm, and J. Wosnitza (2009).Superconducting State in a Gallium-Doped Germanium Layer at Low Temperatures. Physical Review Letters, 102, pp. 217003-217006.[9] Vijay Kumar, and Yoshiyuki Kawazoe (2002). Metal-Encapsulated Caged Clusters of Germanium with Large Gaps and Different Growth Behavior than Silicon. Physical Review Letters, 88, pp. 235504-235507.[10] Xiao-Jiao Deng, Xiang-Yu Kong, Hong-Guang Xu, Xi-Ling Xu, Gang Feng, and Wei-Jun Zheng (2015). Photoelectron Spectroscopy and Density Functional Calculations of VGen- (n = 3 − 12) Clusters. The Journal of Physical Chemistry C, 119 (20), pp. 11048-11055.[11] John P. Perdew, Kieron Burke, and Matthias Ernzerhof (1996).Generalized Gradient Approximation Made Simple. Physical Review Letters, 77, pp. 3865-3868.[12] Chaouki Siouani, Sofiane Mahtout, Sofiane Safer, and Franck Rabilloud (2017).Structure, Stability and Electronic and Magnetic Properties of VGen (n = 1 - 19) Clusters. The Journal of Physical Chemistry A, 121 (18), pp. 3540-3554.[13] Jin Wang, and Ju-Guang Han (2006).A Theoretical Study on Growth Patterns of Ni-Doped Germanium Clusters.The Journal of Physical Chemistry B, 110 (15), pp. 7820-7827.[14] Debashis Bandyopadhyay and Prasenjit Sen (2010). Density Functional Investigation of Structure and Stability of Gen and GenNi (n = 1 − 20) Clusters: Validity of the Electron Counting Rule. The Journal of Physical Chemistry A, 114 (4), pp. 1835-1842[15] Soumaia Djaadi, Kamal Eddine Aiadi, and Sofiane Mahtout (2018). Frist Principles Study of Structural, electronic and magnetic properties of (n = 1 - 17) clusters. Journal of Semiconductors, 39 (4), pp. 42001-420013.[16] İskender Muz,Mustafa Kurban,Kazım Şanlıc (2018). Analysis of the Geometrical Properties and Electronic Structure of Arsenide Doped Boron Cluster: Ab-initio approach. Inorganica Chimica Acta, 474, pp. 66-72.[17] Axel D. Becke (1988). Density-functional exchange - energy approximation with correct asymptotic behavior.Physical Review A, 38, pp. 3098-3100.[18] Willard R. Wadt, P. Jeffrey Hay (1985). Ab initio effective core potentials for molecular calculations.Potentials for main group elements Na to Bi.The Journal of Chemical Physics, 82 (1), pp. 284-298.[19] Willard R. Wadt, P. Jeffrey Hay (1985). Ab initio effective core potentials for molecular calculations.Potentials for K to Au including the outermost core orbitals.The Journal of Chemical Physics, 82 (1), pp. 299-310.[20] Willard R. Wadt, P. Jeffrey Hay (1985). Ab initio effective core potentials for molecular calculations. Potentials for the transition metal atoms Sc to Hg. The Journal of Chemical Physics, 82 (1), pp. 270-283.[21] Gabriele Manca, Samia Kahla, Jean-Yves Saillard, Rémi Marchal, Jean-François Halet (2017). Small Ligated Organometallic Pdn Clusters (n = 4 - 12): A DFT Investigation. Journal of Cluster Science, 28 (2), pp. 853-868.[22] Tran Dieu Hang, Huynh Minh Hung, Lam Ngoc Thiem. Hue M. T. Nguyen (2015). Electronic structure and thermochemical properties of neutral and anionic rhodium clusters Rhn, n = 2 – 13. Evolution of structures and stabilities of binary clusters RhmM (M = Fe, Co, Ni; m = 1 – 6). Computational and Theoretical Chemistry, 1068, pp. 30–41.[23] Michael J. Frisch, et al. (2010). Gaussian 09, Revision C.01.Gaussian, Inc., Wallingford CT.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
J. Lütgert ◽  
J. Vorberger ◽  
N. J. Hartley ◽  
K. Voigt ◽  
M. Rödel ◽  
...  

AbstractWe present structure and equation of state (EOS) measurements of biaxially orientated polyethylene terephthalate (PET, $$({\hbox {C}}_{10} {\hbox {H}}_8 {\hbox {O}}_4)_n$$ ( C 10 H 8 O 4 ) n , also called mylar) shock-compressed to ($$155 \pm 20$$ 155 ± 20 ) GPa and ($$6000 \pm 1000$$ 6000 ± 1000 ) K using in situ X-ray diffraction, Doppler velocimetry, and optical pyrometry. Comparing to density functional theory molecular dynamics (DFT-MD) simulations, we find a highly correlated liquid at conditions differing from predictions by some equations of state tables, which underlines the influence of complex chemical interactions in this regime. EOS calculations from ab initio DFT-MD simulations and shock Hugoniot measurements of density, pressure and temperature confirm the discrepancy to these tables and present an experimentally benchmarked correction to the description of PET as an exemplary material to represent the mixture of light elements at planetary interior conditions.


RSC Advances ◽  
2020 ◽  
Vol 10 (52) ◽  
pp. 31535-31546 ◽  
Author(s):  
M. A. Ali ◽  
S. H. Naqib

The structural, electronic, mechanical and thermodynamic properties of (Ti1−xMox)2AlC (0 ≤ x ≤ 0.20) were explored using density functional theory.


2017 ◽  
Vol 8 (2) ◽  
pp. 1631-1641 ◽  
Author(s):  
Chun-Teh Chen ◽  
Francisco J. Martin-Martinez ◽  
Gang Seob Jung ◽  
Markus J. Buehler

A set of computational methods that contains a brute-force algorithmic generation of chemical isomers, molecular dynamics (MD) simulations, and density functional theory (DFT) calculations is reported and applied to investigate nearly 3000 probable molecular structures of polydopamine (PDA) and eumelanin.


2020 ◽  
Vol 22 (8) ◽  
pp. 4626-4631 ◽  
Author(s):  
Gang Zhao ◽  
Shuyi Shi ◽  
Huijuan Xie ◽  
Qiushuang Xu ◽  
Mingcui Ding ◽  
...  

By ab initio molecular dynamics simulations, the newly developed SCAN meta-GGA functional is proved better than the widely used PBE-GGA functional in describing the equation of state of water.


2017 ◽  
Vol 19 (31) ◽  
pp. 20551-20558 ◽  
Author(s):  
Raúl Guerrero-Avilés ◽  
Walter Orellana

The energetics and diffusion of water molecules and hydrated ions (Na+, Cl−) passing through nanopores in graphene are addressed by dispersion-corrected density functional theory calculations and ab initio molecular dynamics (MD) simulations.


2013 ◽  
Vol 138 (23) ◽  
pp. 234504 ◽  
Author(s):  
Mandy Bethkenhagen ◽  
Martin French ◽  
Ronald Redmer

RSC Advances ◽  
2015 ◽  
Vol 5 (68) ◽  
pp. 55458-55467 ◽  
Author(s):  
Ping Lou

Hybrid structures of a zigzag edge BN nanoribbon/single-walled carbon nanotube, have been studied via standard spin-polarized density functional theory (DFT) calculations as well as ab initio molecular dynamics (MD) simulations.


2015 ◽  
Vol 22 (05) ◽  
pp. 1550067 ◽  
Author(s):  
ZAKIRUR-REHMAN ◽  
SARDAR SIKANDAR HAYAT

In this paper, the thermal diffusion behavior of small two-dimensional Ag -islands on Ag (1 1 1) surface has been explored using molecular dynamics (MD) simulations. The approach is based on semi-empirical potentials. The key microscopic processes responsible for the diffusion of Ag 1−5 adislands on Ag (1 1 1) surface are identified. The hopping and zigzag concerted motion along with rotation are observed for Ag one-atom to three-atom islands while single-atom and multi-atom processes are revealed for Ag four-atom and five-atom islands, during the diffusion on Ag (1 1 1) surface. The same increasing/decreasing trend in the diffusion coefficient and effective energy barrier is observed in both the self learning kinetic Monte Carlo (SLKMC) and MD calculations, for the temperature range of 300–700 K. An increase in the value of effective energy barrier is noticed with corresponding increase in the number of atoms in Ag -adislands. A reasonable linear fit is observed for the diffusion coefficient for studied temperatures (300, 500 and 700 K). For the observed diffusion mechanisms, our findings are in good agreement with ab initio density-functional theory (DFT) calculations for Al / Al (1 1 1) while the energy barrier values are in same range as the experimental values for Cu / Ag (1 1 1) and the theoretical values using ab initio DFT supplemented with embedded-atom method for Ag / Ag (1 1 1).


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