Dear Ali,
First of all, note that the GWW is implemented only at the gamma point,
so it requires large supercells, (or better it is appropriate for
non-crystalline systems).
However the long-range parts of the symmetric dielectric matrix
and of the screened-interaction can be calculated using k-po
Dear Hanghui,
> I did the test to check the forces and stress in the Berry phase
> method with the ultrasoft pseudopotential. The forces are correct but the
> stress is around 50% smaller. I am not sure whether it is due to the
> ultrasoft pseudopotential or not.
At this moment, With a finite ele
Dear Hanghui,
the present version of pw.x does not support yet the calculation
of stress in the presence of an electric field with ultrasoft
pseudopotentials, but only with normconserving
pseudopotentials
> If I turn on a 'sawtooth' potential, the code explicitly warns that
> "Presently stress n
Dear Zhang,
> I tried a test calculation of the dipole moment of water. The water molecule
> is put into a 20 a.u. ^3 box. The relevant setting are
>
> lelfield = .true.
> efield = 0.01
>
> In the output file, it reports
>
> Electronic Dipole per cell (a.u.) -1.921145549061207
> Ionic D
Dear Chen,
The electric field is treated in Rydberg atomic units in pw.x
in this way:
1)The polarization P(\Psi) is calculated as sqrt(2.)*<\Psi|r|\Psi>/Omega
where \Psi is the slater determinant of the KS wavefunctions, Omega is
the valume of the simulation cell,
and the expectation value of th
Dear Chen,
> I am now running a calculation of strained STO and try to calculate
> its spontaneous polarization based on Berry phase method. I try two
> different ways:
> 1) run a self-consistent calculation turning on lelfield=.true. and set
> efield=0.0
> 2) first run a self-consistent calculat
Dear Alan,
>I have two questions about finite electric field calculation based on
> Berry phase.
> First, I have found in the source code that the formula to calcuate the
> polarization in the presence of finite electric field is different in
> Version 4.0 from in Version 3.2. A couple of
Dear Mansoureh
this messages reports the fact that during a single cg minimizationstep,
the lowest energy which is found is that which corresponds to the
trial step. If this happens close to convergence it can be ignored.
Regards,
Paolo Umari
>
> Dear all
> I am running
Dear Jess,
It could be that k points where not string along the same direction
defined by gdir,
In the sense, let's suppose nppstr=3
if gdir=3, you should have something as
K_POINTS (crystal)
N number of total k_points
0. 0. 0. 1.
0. 0. 0.33 1.
0. 0. 0.66 1.
0.5 0. 0.
Dear Ismail,
You are right the ionic term on the atomic forces was missing.
At the moment the Berry's phase electric field is supposed to work
without using the symmetry of the k-points (option: nosym=.true. ).
With the CVS version the options gdir=1 and gdir=2 should work
also on parallel machin
Dear Peter,
I would suggest for checking pw.x the option
diagonalization='cg', in this way a conjugate-gradient
algorithm is used for finding the ground-state of the
KS-Hamiltonian, instead of the 'davidson' algorithm.
It will be slower but maybe more stable.
The main difference between the cp.x
Dear Peter,
If you have to deal with large systems in a supercell
sampled only at the gamma point, you could perform
ionic relaxation using the CPV code cp.x.
For this task you should peform a damped molecular dynamics,
using either a Car-Parrinello or a Born-Oppenheimer
scheme, (the latter should
12 matches
Mail list logo
