Equation of state and phase diagram of ammonia at high pressures from ab initio simulations

2013 ◽  
Vol 138 (23) ◽  
pp. 234504 ◽  
Author(s):  
Mandy Bethkenhagen ◽  
Martin French ◽  
Ronald Redmer
Keyword(s):  
Phase Diagram ◽  
Equation Of State ◽  
Ab Initio ◽  
High Pressures ◽  
Ab Initio Simulations

scholarly journals Effect of salt on the H-bond symmetrization in ice

2015 ◽  
Vol 112 (27) ◽  
pp. 8216-8220 ◽  
Author(s):  
Livia Eleonora Bove ◽  
Richard Gaal ◽  
Zamaan Raza ◽  
Adriaan-Alexander Ludl ◽  
Stefan Klotz ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Hydrogen Bond ◽  
Raman Spectroscopy ◽  
Ab Initio ◽  
High Pressures ◽  
Ab Initio Simulations ◽  
Ice Lattice ◽  
The Universe ◽  
Very High ◽  
Atomic Phase

The richness of the phase diagram of water reduces drastically at very high pressures where only two molecular phases, proton-disordered ice VII and proton-ordered ice VIII, are known. Both phases transform to the centered hydrogen bond atomic phase ice X above about 60 GPa, i.e., at pressures experienced in the interior of large ice bodies in the universe, such as Saturn and Neptune, where nonmolecular ice is thought to be the most abundant phase of water. In this work, we investigate, by Raman spectroscopy up to megabar pressures and ab initio simulations, how the transformation of ice VII in ice X is affected by the presence of salt inclusions in the ice lattice. Considerable amounts of salt can be included in ice VII structure under pressure via rock–ice interaction at depth and processes occurring during planetary accretion. Our study reveals that the presence of salt hinders proton order and hydrogen bond symmetrization, and pushes ice VII to ice X transformation to higher and higher pressures as the concentration of salt is increased.

scholarly journals Ab initio Determination of the Phase Diagram of CO2 at High Pressures and Temperatures

2020 ◽  
Vol 124 (9) ◽  
Author(s):  
Beatriz H. Cogollo-Olivo ◽  
Sananda Biswas ◽  
Sandro Scandolo ◽  
Javier A. Montoya
Keyword(s):  
Phase Diagram ◽  
Ab Initio ◽  
High Pressures ◽  
High Pressures And Temperatures

Phase diagram and equation of state of TiH2 at high pressures and high temperatures

2013 ◽  
Vol 546 ◽  
pp. 270-274 ◽  
Author(s):  
Naruki Endo ◽  
Hiroyuki Saitoh ◽  
Akihiko Machida ◽  
Yoshinori Katayama ◽  
Katsutoshi Aoki
Keyword(s):  
Phase Diagram ◽  
Equation Of State ◽  
High Temperatures ◽  
High Pressures

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

2021 ◽  
Author(s):  
Mandy Bethkenhagen ◽  
Jean-Alexis Hernandez ◽  
Alessandra Benuzzi-Mounaix ◽  
Frederic Datchi ◽  
Martin French ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Equation Of State ◽  
Ab Initio ◽  
Density Functional ◽  
Md Simulations ◽  
Physical Review ◽  
Gradual Transition ◽  
Chemical Physics ◽  
Ab Initio Simulations ◽  
Plasma State

<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>

Phase diagram and equation of state of praseodymium at high pressures and temperatures

2003 ◽  
Vol 67 (13) ◽  
Author(s):  
Bruce J. Baer ◽  
Hyunchae Cynn ◽  
Valentin Iota ◽  
Choong-Shik Yoo ◽  
Guoyin Shen
Keyword(s):  
Phase Diagram ◽  
Equation Of State ◽  
High Pressures ◽  
High Pressures And Temperatures

New developments in the ab initio determination of transition metal alloys phase diagram

1993 ◽  
Vol 90 ◽  
pp. 249-254 ◽  
Author(s):  
C Wolverton ◽  
M Asta ◽  
S Ouannasser ◽  
H Dreyssé ◽  
D de Fontaine
Keyword(s):  
Phase Diagram ◽  
Transition Metal ◽  
Ab Initio ◽  
Metal Alloys ◽  
New Developments ◽  
Transition Metal Alloys
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