Transcript Document

Quantum-chemistry evidence of metallic FCC
fullerite[60] under high pressure
S.S.Moliver
State University of Ulyanovsk, Russia
Aim: Quantum chem. of insulator-metal transition.
• structure model of the high-pressure FCC close
packing with [r5+r5] contacts of unbroken C60s.
• open-shell restricted Hartree-Fock-Roothaan
method, configurations t2, t4, t6; terms.
• calculations with the large-unit-cell model of the
crystal.
Conclusion: rapid uniform compression, faster than
atomic movements performing low-dimensional
topochemical polymerization, may lead to FCC Th
metallic phase.
R interfullerene
distance governs
[r5+r5] cycloaddition.
V optimizes bond
angles of 4-coordinated atom.
W adjusts [2+2] cycle.
U back bond.
• Crystalline class Th demands to insert fullerene
into cube as the emblem shows.
• St.Peter & Paul’s cathedral ascends along [001].
• FCC translations are [101] etc.
• All [111] coinside with C3 axes of fullerene.
• General expression for the total-energy part
Eopen=f2∑{2AJ <t′t″|g|t′t″>-AK <t′t″|g|t″t′>}+
+f2∑AI <t′t′|g|t′t′>,
f=ne/2n
• Selection of determinants for terms, e.g.
γ=(T,1), S=1, M=0:
Â{…, t2 , t3β}+Â{…, t2β, t3 }=(t2t3-t3t2)( β+β )(…)
• Symmetrized coulomb, exchange, self-action:
J=∑<t′t″|g|t′t″>/n(n-1)
K=∑<t′t″|g|t″t′>/n(n-1)
I=∑<t′t′|g|t′t′>/n
• vdW
• [r5+r5]
• [r6+r6]
R=100%
R=80%
R=90%
pristine fullerite
our structure
1D and 2D HPHT polymers.
t4:
{…t6|t0a0…} → {…t4t0a2…}
V=W=U=0
t2:
{…t6a2t2t0…}
V~0.02R
• Atomic shifts V are caused mainly by covalent
reasons, it is stabilization of the valence angle of 4coordinated atom at the end of r5
• Total energy stabilization by atomic shifts W, U is
much less significant, of the order of t4 multiplet
splitting
• Independent self-consistent calculations of total
energies and molecular orbitals of closed-shell
(insulator)
and
open-shell
(metal)
electron
configurations.
Prediction of metallicity
• DFT: electron band structure and density of states are
calculated self-consistently, as well as the occupation
of the bands by a fixed number of electrons. It is
unknown in the beginning, whether the output will be
insulator or metal, and there is no independent test
for both possibilities. This contradicts the DFT
methodology to apply different E[n] to metals and
insulators.
• MO LCAO: the 0-th approximation MOs may be taken
in any configuration. The choice of certain open-shell
term means certain combination of determinants, so
self-consistent field for metal effectively differs from
that for insulator.