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Subject: search.filters.subject.First principles calculations

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    Structural and electronic properties of β-CuPc: First principles study
    (2016-01-01)
    Nuleg, Witoon
    ;
    Thanomngam, Pitiporn
    ;
    Phacheerak, Kanoknan Sarasamak
    Structural and electronic properties of CuPc in β structure (β-CuPc) were investigated by first principles calculations. The generalized gradient approximation (GGA) was used to describe the exchange-correlation with the projector-augmented wave (PAW) method. Under ambient pressure, the calculated structural parameters were calculated and found to be in good agreement with other experimental and theoretical values. The calculated direct band gap was found to be 0.683 eV. The results of electronic properties under various pressures were presented. To investigate the properties under pressure, β-CuPc was calculated at several reduced volumes. It was found that the energy gap decreases when the pressure increases. The behaviors of electronic properties under pressure were also discussed.
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    First principles calculations on crystal and electronic structure of Co2P4O12
    (2014-09-02)
    Rerksompus, Pathompong
    ;
    Sarasamak, Kanoknan
    ;
    Boonchom, Banjong
    ;
    Thanomngam, Pitiporn
    Crystal and electronic structure of violet-pink Co<inf>2</inf>P <inf>4</inf>O<inf>12</inf> have been investigated using first principles calculations based on density functional theory. Its theoretical X-ray diffraction and X-ray absorption fine structure spectra were calculated and compared with their experimental spectra to verify its monophasic. The calculated spectra are in good agreement with the experimental data giving parameters of a = 11.993 Å, b = 8.328 Å, c = 10.150 Å and β = 118.51°. Our calculations on band structure and density of states of Co<inf>2</inf>P<inf>4</inf>O<inf>12</inf> showed that its major electronic transition is associated with internal Co-3d. The calculations indicated that Co<inf>2</inf>P<inf>4</inf>O<inf>12</inf> is a half metal ferromagnetic material which disagreed with the experimental knowledge. © 2014 Taylor & Francis Group, LLC.
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    First principles calculations of elastic properties under pressure in SiC
    (2010-04-20)
    Sarasamak, Kanoknan
    ;
    Limpijumnong, Sukit
    ;
    Lambrecht, Walter R.L.
    First principles density functional theory is employed to study the elastic constants and sound velocities in wurtzite-SiC under pressure. The focus is on the behavior of the elastic constants (C<inf>ij</inf>) and sound velocities (Cij/ρ) as a function of pressure. The pressure dependences of the transverse acoustic modes in sound velocities which correspond to the wurtzite to rocksalt phase transformation is analyzed. We found that the phase transformation from wurtzite to rocksalt structure relates to an orthorhombic strain with two components: (1) a traceless compression along the [0 0 0 1] axis which corresponds to the sound velocity C44/ρ and (2) a traceless compression along [011̄0] direction which corresponds to the sound velocity C66/ρ. © 2010 Elsevier B.V. All rights reserved.