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Title: Structural inheritance and difference between Ti 2AlC, Ti 3AlC 2  and Ti 5Al 2C 3 under pressure from first principles

The structural inheritance and difference between Ti 2AlC, Ti 3AlC 2 and Ti 5Al 2C 3 under pressure from first principles are studied. The results indicate that the lattice parameter a are almost the same within Ti 2AlC, Ti 3AlC 2 and Ti 5Al 2C 3, and the value of c in Ti 5Al 2C 3 is the sum of Ti 2AlC and Ti 3AlC 2 which is revealed by the covalently bonded chain in the electron density difference: Al–Ti–C–Ti–Al for Ti 2AlC, Al–Ti 2–C–Ti 1–C–Ti 2–Al for Ti 3AlC 2 and Al–Ti 3–C 2–Ti 3–Al–Ti 2–C 1–Ti 1–C 1–Ti 2–Al for Ti 5Al 2C 3. The calculated axial compressibilities, volumetric shrinkage, elastic constant c 11, c 33/c 11 ratio, bulk modulus, shear modulus, and Young’s modulus of Ti 5Al 2C 3 are within the range of the end members (Ti 2AlC and Ti 3AlC 2) in a wide pressure range of 0–100 GPa. Only Ti 2AlC is isotropic crystal at about 50 GPa within the Ti–Al–C compounds. All of the Ti 3 d density of states curves of the three compounds move from lower energy to higher energy level with pressure increasing. The similarities of respective bond length, bondmore » overlap population (Ti–C, Ti–Al and Ti–Ti), atom Mulliken charges under pressure as well as the electron density difference for the three compounds are discovered. Among the Ti–Al–C ternary compounds, Ti–Ti bond behaves least compressibility, whereas the Ti–Al bond is softer than that of Ti–C bonds, which can also been confirmed by the density of states and electron density difference. Bond overlap populations of Ti–Ti, Ti–C and Ti–Al indicate that the ionicity interaction becomes more and more stronger in the three structures as the pressure increasing. Lastly, Mulliken charges of Ti 1, Ti 2, Ti 3, C and Al are 0.65, 0.42, 0.39, –0.73, –0.04 at 0 GPa, respectively, which are consistent with the Pauling scale.« less
Authors:
 [1] ;  [2] ;  [3]
  1. Northeastern Univ., Shenyang (China); Liaoning Univ. of Traditional Chinese Medicine, Shenyang (China)
  2. Northeastern Univ., Shenyang (China)
  3. Zhejiang Univ. of Technology, Hangzhou (China); Ames Lab. and Iowa State Univ., Ames, IA (United States)
Publication Date:
Report Number(s):
IS-J-9366
Journal ID: ISSN 0217-9849
Grant/Contract Number:
AC02-07CH11358
Type:
Accepted Manuscript
Journal Name:
Modern Physics Letters B
Additional Journal Information:
Journal Volume: 31; Journal Issue: 03; Journal ID: ISSN 0217-9849
Publisher:
World Scientific Publishing
Research Org:
Ames Lab., Ames, IA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; first principles; high pressure; nanolaminate
OSTI Identifier:
1374746