scholarly journals A room-temperature ferroelectric semimetal

2019 ◽  
Vol 5 (7) ◽  
pp. eaax5080 ◽  
Author(s):  
Pankaj Sharma ◽  
Fei-Xiang Xiang ◽  
Ding-Fu Shao ◽  
Dawei Zhang ◽  
Evgeny Y. Tsymbal ◽  
...  
Keyword(s):  
First Principles ◽  
Electrical Transport ◽  
Room Temperature ◽  
Electric Polarization ◽  
First Principles Calculations ◽  
New Class ◽  
Weyl Semimetal ◽  
Ferroelectric Domain Structure ◽  
Ferroelectric Domains ◽  
Crystalline Metal

Coexistence of reversible polar distortions and metallicity leading to a ferroelectric metal, first suggested by Anderson and Blount in 1965, has so far remained elusive. Electrically switchable intrinsic electric polarization, together with the direct observation of ferroelectric domains, has not yet been realized in a bulk crystalline metal, although incomplete screening by mobile conduction charges should, in principle, be possible. Here, we provide evidence that native metallicity and ferroelectricity coexist in bulk crystalline van der Waals WTe2by means of electrical transport, nanoscale piezoresponse measurements, and first-principles calculations. We show that, despite being a Weyl semimetal, WTe2has switchable spontaneous polarization and a natural ferroelectric domain structure at room temperature. This new class of materials has tantalizing potential for functional nanoelectronics applications.

Tuning intrinsic ferromagnetic and anisotropic properties of the Janus VSeS monolayer

2020 ◽  
Vol 8 (38) ◽  
pp. 13286-13296
Author(s):  
Mahsa Abdollahi ◽  
Meysam Bagheri Tagani
Keyword(s):  
Magnetic Properties ◽  
Curie Temperature ◽  
First Principles ◽  
2D Materials ◽  
High Curie Temperature ◽  
First Principles Calculations ◽  
Ferromagnetic Properties ◽  
Anisotropic Properties ◽  
Electronic And Magnetic Properties ◽  
New Class

Motivated by the intrinsic ferromagnetic properties and high Curie temperature of V-based Janus dichalcogenide monolayers as a new class of 2D materials, we investigated the structural, electronic and magnetic properties of the Janus VSeS monolayer by first-principles calculations.

Where Should We Look For High Zt Materials: Suggestions From Theory.

2000 ◽  
Vol 626 ◽  
Author(s):  
M. Fornari ◽  
D. J. Singh ◽  
I. I. Mazin ◽  
J. L. Feldman
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
First Principles ◽  
Room Temperature ◽  
First Principles Calculations ◽  
High Electrical Conductivity ◽  
Bulk Materials ◽  
Low Thermal Conductivity ◽  
Computational Exploration ◽  
Single Material

ABSTRACTThe key challenges in discovering new high ZT thermoelectrics are understanding how the nearly contradictory requirements of high electrical conductivity, high thermopower and low thermal conductivity can be achieved in a single material and based on this identifying suitable compounds. First principles calculations provide a material specific microscopic window into the relevant properties and their origins. We illustrate the utility of the approach by presenting specific examples of compounds belonging to the class of skutterudites that are or are not good thermoelectrics along with the microscopic reasons. Based on our computational exploration we make a suggestion for achieving higher values of ZT at room temperature in bulk materials, namely n-type La(Ru,Rh)4Sb12 with high La-filling.

scholarly journals Phase Stability in U-6Nb Alloy Doped with Ti from the First Principles Theory

2020 ◽  
Vol 10 (10) ◽  
pp. 3417
Author(s):  
Alexander Landa ◽  
Per Söderlind ◽  
Amanda Wu
Keyword(s):  
Phase Stability ◽  
First Principles ◽  
Density Functional ◽  
Room Temperature ◽  
Rapid Quenching ◽  
Quantum Mechanical ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Effect Of Impurities

First-principles calculations within the density-functional-theory (DFT) approach are conducted in order to explore and explain the effect of small amounts of titanium on phase stability in the U-6Nb alloy. During rapid quenching from high to room temperature, metastable phases α′ (orthorhombic), α″ (monoclinic), and γ0 (tetragonal) can form, depending on Nb concentration. Important mechanical properties depend on the crystal structure and, therefore, an understanding of the effect of impurities on phase stability is essential. Insights on this issue are obtained from quantum-mechanical DFT calculations. The DFT framework does not rely on any material-specific assumptions and is therefore ideal for an unbiased investigation of the U-Nb system.

Disparate strain response of the thermal transport properties of bilayer penta-graphene as compared to that of monolayer penta-graphene

2019 ◽  
Vol 21 (28) ◽  
pp. 15647-15655 ◽  
Author(s):  
Zhehao Sun ◽  
Kunpeng Yuan ◽  
Xiaoliang Zhang ◽  
Guangzhao Qin ◽  
Xiaojing Gong ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Transport Equation ◽  
First Principles ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Boltzmann Transport Equation ◽  
Strain Response ◽  
First Principles Calculations ◽  
Boltzmann Transport ◽  
Strain Modulation

In this study, strain modulation of the lattice thermal conductivity of monolayer and bilayer penta-graphene (PG) at room temperature was investigated using first-principles calculations combined with the phonon Boltzmann transport equation.

Reaction mechanism of metal and pyrite under HPHT conditions and improvement of the properties

2022 ◽  
Author(s):  
Yao Wang ◽  
Dan Xu ◽  
Shan Gao ◽  
Qi Chen ◽  
Dayi Zhou ◽  
...  
Keyword(s):  
Thermal Stability ◽  
High Pressure ◽  
Reaction Mechanism ◽  
First Principles ◽  
Room Temperature ◽  
First Principles Calculations ◽  
Mine Wastewater ◽  
Al Addition ◽  
Thermal Stability Of ◽  
Pyrite Tailings

Abstract Pyrite tailings are the main cause of acid mine wastewater. An idea was put forward to more effectively use pyrite, and it was modified by exploiting the reducibility of metal represented by Al under high-pressure and high-temperature (HPHT) conditions. Upon increasing the Al addition, the conductivity of pyrite were effectively improved, which is nearly 734-times higher than that of unmodified pyrite at room temperature. First-principles calculations were used to determine the influence of a high pressure on the pyrite lattice. The high pressure increased the thermal stability of pyrite, reduced pyrite to high-conductivity Fe7S8 (pyrrhotite) by Al, and prevented the formation of iron. Through hardness and density tests the influence of Al addition on the hardness and toughness of samples was explored. Finally the possibility of using other metal-reducing agents to improve the properties of pyrite was discussed.

Dirac–Weyl semimetal phase in noncentrosymmetric transition metal monochalcogenides MoTe and WTe

2019 ◽  
Vol 7 (39) ◽  
pp. 12151-12159 ◽  
Author(s):  
Lijun Meng ◽  
Jiafang Wu ◽  
Yizhi Li ◽  
Jianxin Zhong
Keyword(s):  
Transition Metal ◽  
First Principles ◽  
Tight Binding ◽  
Low Energy ◽  
Effective Model ◽  
First Principles Calculations ◽  
Topological Properties ◽  
Weyl Semimetal ◽  
Tight Binding Method

We investigated the topological properties of hexagonal transition metal monochalcogenides (TMMs) MoTe and WTe by combining first-principles calculations, the Wannier-based tight-binding method and the low energy k·p effective model.

scholarly journals Structural transitions in Pb(In1∕2Nb1∕2)O3 under pressure

2015 ◽  
Vol 05 (04) ◽  
pp. 1550033 ◽  
Author(s):  
Muhtar Ahart ◽  
Maddury Somayazulu ◽  
Seiji Kojima ◽  
Naohiko Yasuda ◽  
Sergey Prosandeev ◽  
...  
Keyword(s):  
Structural Change ◽  
Ground State ◽  
First Principles ◽  
Room Temperature ◽  
First Principles Calculations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Patterns ◽  
Pressure Evolution ◽  
Linear Compressibility

Room-temperature Raman scattering and x-ray diffraction measurements together with first-principles calculations were employed to investigate the behavior of disordered Pb(In[Formula: see text]Nb[Formula: see text]O3 (PIN) under pressure up to 50[Formula: see text]GPa. Raman spectra show broad bands but a peak near the 380[Formula: see text]cm[Formula: see text] increases its intensity with pressure. The linewidth of the band at 550[Formula: see text]cm[Formula: see text] also increases with pressure, while two of the Raman peaks merge above 6[Formula: see text]GPa. Above 16[Formula: see text]GPa, we observe additional splitting of the band at 50[Formula: see text]cm[Formula: see text]. The pressure evolution of the diffraction patterns for PIN shows obvious Bragg peaks splitting above 16[Formula: see text]GPa; consistent with a symmetry lowering transition. The transition at 0.5[Formula: see text]GPa is identified as a pseudo-cubic to orthorhombic (Pbam) structural change whereas the transition at 16[Formula: see text]GPa is isostructure and associated with changes in linear compressibility and octahedral titling, and the transition at 30[Formula: see text]GPa is associated to an orthorhombic to monoclinic change. First-principles calculations indicate that the Pbam structure is ground state with antiferrodisdortion consistent with experiment.

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