BAND STRUCTURE, METALLIZATION, AND SUPERCONDUCTIVITY OF GaAs AND InAs UNDER HIGH PRESSURE

2007 ◽  
Vol 06 (04) ◽  
pp. 833-843 ◽  
Author(s):  
A. AMALRAJ ◽  
C. NIRMALA LOUIS ◽  
SR. GERARDIN JAYAM
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Band Structure ◽  
Structural Phase Transition ◽  
Electronic Band Structure ◽  
Structural Phase ◽  
Normal Structure ◽  
Superconducting Transition ◽  
Electronic Band ◽  
Phase Transition Pressure

The electronic band structure, metallization, structural phase transition, and superconductivity of cubic zinc blende type GaAs and InAs are investigated. The equilibrium lattice constant, bulk modulus, and the phase transition pressure at which the compounds undergo structural phase transition from ZnS to NaCl are predicted from the total energy calculations. The density of states at the Fermi level (N(E F )) get enhanced after metallization, which leads to the superconductivity in GaAs and InAs . The superconducting transition temperatures (T c ) of GaAs and InAs are obtained as a function of pressure for both the ZnS and NaCl structures. GaAs and InAs come under the class of pressure-induced superconductors. When pressure is increased T c increases in both the normal and high pressure-structures. The dependence of T c on electron–phonon mass enhancement factor λ shows that GaAs and InAs are electron–phonon-mediated superconductors. Also, it is found that GaAs and InAs retained in their normal structure under high pressure give appreciably high T c .

BAND STRUCTURE, METALLIZATION AND SUPERCONDUCTIVITY OF InP AND InN UNDER HIGH PRESSURE

2012 ◽  
Vol 11 (01) ◽  
pp. 19-33 ◽  
Author(s):  
A. AMAL RAJ ◽  
C. NIRMALA LOUIS ◽  
V. REJILA ◽  
K. IYAKUTTI
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Band Structure ◽  
Structural Phase Transition ◽  
Electronic Band Structure ◽  
Indium Nitride ◽  
Structural Phase ◽  
Superconducting Transition ◽  
Electronic Band ◽  
Lmto Method

The electronic band structure, structural phase transition, metallization and superconducting transition of cubic zinc blende type indium phosphide (InP) and indium nitride (InN), under pressure, are studied using FP-LMTO method. These indium compounds become metals and superconductors under high pressure but before that they undergo structural phase transition from ZnS to NaCl structure. The ground state properties and band gap values are compared with the experimental and previous theoretical results. From our analysis, it is found that the metallization pressure increases with increase of lattice constant. The superconducting transition temperatures (Tc) of InP and InN are obtained as a function of pressure for both the ZnS and NaCl structures and these compounds are identified as pressure induced superconductors. When pressure is increased Tc increases in both the normal ( ZnS ) and high pressure ( NaCl ) structures. The dependence of Tc on electron–phonon mass enhancement factor λ shows that InP and InN are electron–phonon mediated superconductors. The non-occurrence of metallization, phase transition and onset of superconductivity simultaneously in InP and InN is confirmed.

PRESSURE-INDUCED METALLIZATION AND SUPERCONDUCTIVITY IN InP AND InN

2011 ◽  
Vol 25 (04) ◽  
pp. 573-587
Author(s):  
K. IYAKUTTI ◽  
V. REJILA ◽  
M. RAJARAJESWARI ◽  
C. NIRMALA LOUIS ◽  
S. MAHALAKSHMI
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Structural Phase Transition ◽  
Electronic Band Structure ◽  
Indium Nitride ◽  
Structural Phase ◽  
Superconducting Transition ◽  
Electronic Band ◽  
Zinc Blende ◽  
Lmto Method

The electronic band structure, structural phase transition, metallization and superconducting transition of cubic zinc blende-type indium phosphide ( InP ) and indium nitride ( InN ), under pressure, are studied using TB-LMTO method. These indium compounds become metals and superconductors under high pressure but before that they undergo structural phase transition from ZnS to NaCl structure. The ground-state properties and band gap values are compared with the experimental and previous theoretical results. From our analysis, it is found that the metallization pressure increases with increase of lattice constant. The superconducting transition temperatures (Tc) of InP and InN are obtained as a function of pressure for both the ZnS and NaCl structures and these compounds are identified as pressure-induced superconductors. When pressure is increased Tc increases in both the normal ( ZnS ) and high pressure ( NaCl ) structures. The dependence of Tc on electron–phonon mass enhancement factor λ shows that InP and InN are electron–phonon mediated superconductors. The non-occurrence of metallization, phase transition and onset of superconductivity simultaneously in InP and InN are confirmed.

PRESSURE INDUCED STRUCTURAL PHASE TRANSITION AND SUPERCONDUCTIVITY IN TITANIUM METAL

2009 ◽  
Vol 08 (01) ◽  
pp. 85-99
Author(s):  
A. AMAL RAJ
Keyword(s):  
Phase Transition ◽  
Band Structure ◽  
Density Of States ◽  
Structural Phase Transition ◽  
High Pressures ◽  
Structural Phase ◽  
Normal Pressure ◽  
Present Calculation ◽  
Superconducting Transition ◽  
Electronic Band

The electronic band structure, density of states, structural phase transition, and superconducting transition temperature under normal and high pressures are reported for titanium ( Ti ). The normal pressure band structure and density of states of hcp- Ti agree well with the previous calculations. The high pressure band structure exhibits significant deviations from the normal pressure band structure due to s, p → d transition. On the basis of band structure and total energy results obtained using full potential linear muffin-tin orbital method (FP LMTO), we predict a phase transformation sequence of α (hcp) → ω (hexagonal) → γ (distorted hcp) → β (bcc) in titanium under pressure. From our analysis we predict a δ (distorted bcc) phase which is not stable at any high pressures. According to the present calculation, at normal pressure, the superconducting transition of hcp- Ti occurs at 0.36 K which is in agreement with the experimental observation of 0.4 K. When the pressure is increased, it is predicted that, Tc increases at a rate of 3.123 K/Mbar in hcp- Ti . On further increase of pressure Tc begins to decrease at a rate of 1.464 K/Mbar.

PRESSURE-INDUCED ELECTRONIC PHASE TRANSITIONS AND SUPERCONDUCTIVITY IN TITANIUM

2009 ◽  
Vol 23 (05) ◽  
pp. 723-741 ◽  
Author(s):  
K. IYAKUTTI ◽  
C. NIRMALA LOUIS ◽  
S. ANURATHA ◽  
S. MAHALAKSHMI
Keyword(s):  
High Pressure ◽  
Band Structure ◽  
Fermi Surface ◽  
High Pressures ◽  
Ambient Pressure ◽  
Structural Phase ◽  
Normal Pressure ◽  
Orbital Method ◽  
Superconducting Transition ◽  
Electronic Band

The electronic band structure, density of states, structural phase transition, superconducting transition and Fermi surface cross section of titanium ( Ti ) under normal and high pressures are reported. The high pressure band structure exhibits significant deviations from the normal pressure band structure due to s → d transition. On the basis of band structure and total energy results obtained using tight-binding linear muffin-tin orbital method (TB LMTO), we predict a phase transformation sequence of α( hcp ) → ω (hexagonal) → γ (distorted hcp) → β (bcc) in titanium under pressure. From our analysis, we predict a δ (distorted bcc) phase which is not stable at any high pressures. At ambient pressure, the superconducting transition occurs at 0.354 K. When the pressure is increased, it is predicted that, Tc increases at a rate of 3.123 K/Mbar in hcp–Ti . On further increase of pressure, Tc begins to decrease at a rate of 1.464 K/Mbar. The highest value of Tc(P) estimated is 5.043 K for hcp–Ti , 4.538 K for ω– Ti and 4.85 K for bcc – Ti . From this, it is inferred that the maximum value of Tc(P) is rather insensitive to the crystal structure of Ti . The nonlinearities in Tc(P) is explained by considering the destruction and creation of new parts of Fermi surface at high pressure. At normal pressure, the hardness of Ti is in the following order: ω- Ti > hcp - Ti > bcc- Ti > γ- Ti .

scholarly journals Structural phase transition and photoluminescence properties of wurtzite CdS:Eu3+ nanoparticles under high pressure

RSC Advances ◽  
2017 ◽  
Vol 7 (50) ◽  
pp. 31433-31440 ◽  
Author(s):  
Rui Zhao ◽  
Tianye Yang ◽  
Yang Luo ◽  
Mingyan Chuai ◽  
Xiaoxin Wu ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Cds Nanoparticles ◽  
Pressure Probe ◽  
Photoluminescence Properties ◽  
Rocksalt Structure ◽  
Phase Transition Pressure ◽  
The Eu

Eu dopant increases the phase transition pressure from wurtzite to rocksalt structure compared with CdS nanoparticles. The PL peaks of the Eu3+ ions can used as pressure probe after the quenching of the PL peaks of rocksalt structure CdS.

High-Pressure Structural Phase Transition in MgxCd1-xO Compounds

2016 ◽  
Vol 28 ◽  
pp. 77-84
Author(s):  
Saligram Verma ◽  
Arvind Jain ◽  
Kamal Kumar Choudhary ◽  
Netram Kaurav
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Physical Properties ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Repulsive Interaction ◽  
Interionic Interaction ◽  
Phase Transition Pressure ◽  
Cscl Structure ◽  
Physical Interactions

The high-pressure technique is useful to understand physical properties because the technique can directly control bond length and phase transition. As a general trend, the pressure-induced phase transition causes an increase of coordination number with a drastic change of their physical properties. Here, we attempt to explore the pressure-induced phase transitions from the sixfold-coordinated NaCl structure (B1) to the eightfold-coordinated CsCl structure (B2) in MgxCd1−xO by applying an effective interionic interaction potential, which includes the long range Coulomb, van der Waals (vdW) interaction and the short-range repulsive interaction upto second-neighbor ions within the Hafemeister and Flygare approach. Assuming that both the ions are polarizable, the Slater-Kirkwood variational method is employed to estimate the vdW coefficients for parent compounds. The estimated values of the phase transition pressure (Pt) increase with Mg concentration. The vast volume discontinuity in pressure volume phase diagram identifies the structural phase transition from B1 to B2 structure. The results obtain from the present calculations requires the complete understanding of many physical interactions that are essential to ternary oxides, containing elements with size and chemical mismatch, will lead to a consistent explanation of the documented structural properties.

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