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The structure of solid oxygen has been studied at pressures from 50 to 140~GPa using static structure search methods and molecular dynamics simulations with density functional theory and a hybrid exchange functional. Several crystalline…

Materials Science · Physics 2023-09-26 Sabri F. Elatresh , V. Askarpour , S. A. Bonev

Experimental progress finally reached the metallic solid hydrogen phase, which was predicted by Wigner and Huntington over 80 years ago. However, the different structures in the phase diagram are still been debated due to the difficulty of…

Materials Science · Physics 2022-01-03 Tom Ichibha , Yunwei Zhang , Kenta Hongo , Ryo Maezono , Fernando A. Reboredo

Alkali halides $MX$, have been viewed as typical ionic compounds, characterized by 1:1 ratio necessary for charge balance between M$^+$ and X$^-$. It was proposed that group I elements like Cs can be oxidized further under high pressure.…

Materials Science · Physics 2019-01-03 Qiang Zhu , Artem R. Oganov , Qingfeng Zeng

With the motivation of searching for new superconductors in the Mg-B system, we performed ab initio evolutionary searches for all the stable compounds in this binary system in the pressure range of 0-200 GPa. We found previously unknown,…

Superconductivity · Physics 2017-05-24 M. M. Davari Esfahani , Q. Zhu , H. Dong , A. R. Oganov , S. Wang , M. S. Rakitin , X-F. Zhou

We report the discovery of a new allotrope of iron by first principles calculations. This phase has $Pmn2_1$ symmetry, a six-atom unit cell (hence the name Fe$_6$), and the highest magnetization density (M$_s$) among all known crystalline…

We present detailed ab-initio lattice dynamical analysis of the Fe-O infinite-layer compounds CaFeO2 and SrFeO2 in various magnetic configurations. These indicate strong spin-phonon coupling in SrFeO2 in contrast to that in case of CaFeO2.…

Materials Science · Physics 2016-09-13 M. K. Gupta , R. Mittal , S. L. Chaplot , Cedric Tassel , Hiroshi Kageyama

While the tetragonal antiferro-electrically distorted (AFD) phase with space group $I4/mcm$ is well known for SrTiO$_3$ to occur below 105 K, there are also some hints in literature of an orthorhombic phase, either at lower temperature at…

Materials Science · Physics 2018-09-27 Churna Bhandari , Walter R. L. Lambrecht

The pressure-induced transformation of diatomic nitrogen into non-molecular polymeric phases may produce potentially useful high-energy-density materials. We combine first-principles calculations with structure searching to predict a new…

Materials Science · Physics 2015-09-30 Yinwei Li , Jian Hao , Hanyu Liu , Siyu Lu , John S. Tse

We have performed a combined experimental and theoretical study of ethane and methane at high pressures up to 120 GPa at 300 K using x-ray diffraction and Raman spectroscopy and the USPEX ab-initio evolutionary structural search algorithm,…

We synthesized new layered iron arsenide oxides (Fe2As2)(Sr4(Sc,Ti)3O8),(Fe2As2)(Ba4Sc3O7.5), and (Fe2As2)(Ba3Sc2O5). The crystal structures of these compounds are tetragonal with a space group of I4/mmm. The structure of…

Superconductivity · Physics 2010-06-14 Naoto Kawaguchi , Hiraku Ogino , Yasuaki Shimizu , Kohji Kishio , Jun-ichi Shimoyama

Polycrystalline samples of the layered iron arsenides Sr2CrO3FeAs and Ba2ScO3FeAs were synthesized by high temperature solid state reactions and their crystal structures determined by the X-ray powder diffraction. Their structures are…

There have existed for a long time a paradigm that TiO phases at ambient conditions are stable only if structural vacancies are available. Using an evolutionary algorithm, we perform an ab initio search of possible zero-temperature…

Chemical Physics · Physics 2020-03-18 N. M. Chtchelkatchev , R. E. Ryltsev , M. V. Magnitskaya , Andrey A. Rempel

Isolated oxygen impurities and fully oxidized structures of four stable two-dimensional (2D) SiS structures are investigated by {\em ab initio} density functional calculations. Binding energies of oxygen impurities for all the four 2D SiS…

Materials Science · Physics 2019-04-23 Zhengnan Li , Shuai Dong , Jie Guan

First principles density functional calculations for Fe$_{2}$O$_{3}$ has been performed over a wide range of pressures. The ground state is corundum-type hematite and is an antiferromagnetic insulator. This is in good agreement with…

Materials Science · Physics 2009-03-13 Dipta Bhanu Ghosh , Stefano de Gironcoli

The present work reports on the new soft ferromagnetic Heusler phases Fe2NiGe, Fe2CuGa, and Fe2CuAl, which in previous theoretical studies have been predicted to exist in a tetragonal regular Heusler structure. Together with the known…

Materials Science · Physics 2014-04-18 T. Gasi , V. Ksenofontov , J. Kiss , S. Chadov , A. K. Nayak , M. Nicklas , J. Winterlik , M. Schwall , P. Klaer , P. Adler , C. Felser

Using density-functional theory (DFT) we calculate the Gibbs free energy to determine the lowest-energy structure of a RuO_2(110) surface in thermodynamic equilibrium with an oxygen-rich environment. The traditionally assumed stoichiometric…

Materials Science · Physics 2009-11-07 Karsten Reuter , Matthias Scheffler

Using first-principles variable-composition evolutionary methodology, we explored the high-pressure structures of beryllium hydrides between 0 and 400 GPa. We found that BeH$_2$ remains the only stable compound in this pressure range. The…

Materials Science · Physics 2014-07-15 Shuyin Yu , Qingfeng Zeng , Artem R. Oganov , Chaohao Hu , Gilles Frapper , Litong Zhang

We report high pressure structural phase transformation sequence in a layered Iron-based superconducting compound FeSe0.3Te0.7 to 31 GPa at room temperature. The ambient pressure PbO type tetragonal phase (Space Group - P4/nmm) transforms…

Materials Science · Physics 2011-05-05 Andrew K. Stemshorn , Yogesh K. Vohra , Phillip M. Wu , F. C. Hsu , Y. L. Huang , M. K. Wu , K. W. Yeh

A previously unknown thermodynamically stable high-pressure phase of BeF$_{2}$ has been predicted using the evolutionary algorithm USPEX. This phase occurs in the pressure range 18-27 GPa. Its structure has $C2/c$ space group symmetry and…

Based on the unbiased structure prediction, we showed that the stable form of NiSi compound under the pressure of 100 and 200 GPa is the Pmmn-structure. Furthermore, we discovered a new stable phase - the deformed tetragonal CsCl-type…

Materials Science · Physics 2015-04-24 Pavel N. Gavryushkin , Zakhar I. Popov , Konstantin D. Litasov , Alex N. Gavryushkin