[QE-users] Negatively charged isolated molecule

[Ernane de Freitas Martins]

Hello,

I'm experiencing a problem to run a negatively charge molecule in quantum
espresso. The system is CO32-.

I try both vacuum and solvated (environ) calculations. The solvated one
works fine.

The problem is the calculation in vacuum. It never give the first ionic
step because the SCF accuracy never reaches the convence criterion.

I tried many different solutions (increase cutoffs and box size, use assume
isolated, decreasing and changing the mixing scheme and etc) and nothing
works.

The unique calculation that works fine for vacuum is the one with a box
size of 7.9 x 7.9 x 7.9 A. I really don't understand why it only works for
this specific box size.

I ran several other charged systems (+1, +2 and -1 total charge) and all of
them worked fine. The problem appears for -2 total charge in vacuum.

Would some of you kindly help me in this?

Cheers,

Dr. Ernane de Freitas Martins
Postdoctoral researcher
IF - USP
São Paulo, SP - Brazil
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