A

Name ABCapHeight
Section Time-Dependent::Absorbing Boundaries
Type float
Default -0.2 a.u.

When AbsorbingBoundaries = cap, this is the height of the imaginary potential.

Name ABShape
Section Time-Dependent::Absorbing Boundaries
Type block

Set the shape of the absorbing boundaries. Here you can set the inner and outer bounds by setting the block as follows:

%ABShape
   inner | outer | "user-defined"
%

The optional 3rd column is a user-defined expression for the absorbing boundaries. For example, $r$ creates a spherical absorbing zone for coordinates with ${\tt inner} < r < {\tt outer}$, and $z$ creates an absorbing plane. Note, values outer larger than the box size may lead in these cases to unexpected reflection behaviours. If no expression is given, the absorbing zone follows the edges of the box (not valid for user-defined box).

Name AbsorbingBoundaries
Section Time-Dependent::Absorbing Boundaries
Type flag
Default not_absorbing

To improve the quality of the spectra by avoiding the formation of standing density waves, one can make the boundaries of the simulation box absorbing and use exterior complex scaling.

Options:

• not_absorbing:
  Reflecting boundaries.
  
• mask:
  Absorbing boundaries with a mask function.
  
• cap:
  Absorbing boundaries with a complex absorbing potential.
  
• exterior:
  Exterior complex scaling (not yet implemented).
  

Name ABWidth
Section Time-Dependent::Absorbing Boundaries
Type float

Specifies the boundary width. For a finer control over the absorbing boundary shape use ABShape.

Name ACBN0IntersiteCutoff
Section Hamiltonian::DFT+U
Type float

The cutoff radius defining the maximal intersite distance considered. Only available with ACBN0 functional with intersite interaction.

Name ACBN0IntersiteInteraction
Section Hamiltonian::DFT+U
Type logical
Default no

If set to yes, Octopus will determine the effective intersite interaction V Only available with ACBN0 functional. It is strongly recommended to set AOLoewdin=yes when using the option.

Name ACBN0RotationallyInvariant
Section Hamiltonian::DFT+U
Type logical

If set to yes, Octopus will use for U and J a formula which is rotationally invariant. This is different from the original formula for U and J. This is activated by default, except in the case of spinors, as this is not yet implemented in this case.

Name ACBN0Screening
Section Hamiltonian::DFT+U
Type float
Default 1.0

If set to 0, no screening will be included in the ACBN0 functional, and the U will be estimated from bare Hartree-Fock. If set to 1 (default), the full screening of the U, as defined in the ACBN0 functional, is used.

Name AccelBenchmark
Section Execution::Accel
Type logical
Default no

If this variable is set to yes, Octopus will run some routines to benchmark the performance of the accelerator device.

Name AccelDevice
Section Execution::Accel
Type integer
Default gpu

This variable selects the OpenCL or CUDA accelerator device that Octopus will use. You can specify one of the options below or a numerical id to select a specific device.

Values >= 0 select the device to be used. In case of MPI enabled runs devices are distributed in a round robin fashion, starting at this value.

Options:

• gpu:
  If available, Octopus will use a GPU.
  
• cpu:
  If available, Octopus will use a CPU (only for OpenCL).
  
• accelerator:
  If available, Octopus will use an accelerator (only for OpenCL).
  
• accel_default:
  Octopus will use the default device specified by the implementation. implementation.
  

Name AccelPlatform
Section Execution::Accel
Type integer
Default 0

This variable selects the OpenCL platform that Octopus will use. You can give an explicit platform number or use one of the options that select a particular vendor implementation. Platform 0 is used by default.

This variable has no effect for CUDA.

Options:

• amd:
  Use the AMD OpenCL platform.
  
• nvidia:
  Use the Nvidia OpenCL platform.
  
• ati:
  Use the ATI (old AMD) OpenCL platform.
  
• intel:
  Use the Intel OpenCL platform.
  

Name AdaptivelyCompressedExchange
Section Hamiltonian
Type logical
Default false

(Experimental) If set to yes, Octopus will use the adaptively compressed exchange operator (ACE) for HF and hybrid calculations, as defined in Lin, J. Chem. Theory Comput. 2016, 12, 2242.

Name AllowCPUonly
Section Execution::Accel
Type logical

In order to prevent waste of resources, the code will normally stop when the GPU is disabled due to incomplete implementations or incompatibilities. AllowCPUonly = yes overrides this and allows the code execution also in these cases.

Name AlphaFMM
Section Hamiltonian::Poisson
Type float
Default 0.291262136

Dimensionless parameter for the correction of the self-interaction of the electrostatic Hartree potential, when using PoissonSolver = FMM.

Octopus represents charge density on a real-space grid, each point containing a value $\rho$ corresponding to the charge density in the cell centered in such point. Therefore, the integral for the Hartree potential at point $i$, $V_H(i)$, can be reduced to a summation:

$V_H(i) = \frac{\Omega}{4\pi\varepsilon_0} \sum_{i \neq j} \frac{\rho(\vec{r}(j))}{|\vec{r}(j) - \vec{r}(i)|} + V_{self.int.}(i)$ where $\Omega$ is the volume element of the mesh, and $\vec{r}(j)$ is the position of the point $j$. The $V_{self.int.}(i)$ corresponds to the integral over the cell centered on the point $i$ that is necessary to calculate the Hartree potential at point $i$:

$V_{self.int.}(i)=\frac{1}{4\pi\varepsilon_0} \int_{\Omega(i)}d\vec{r} \frac{\rho(\vec{r}(i))}{|\vec{r}-\vec{r}(i)|}$

In the FMM version implemented into Octopus, a correction method for $V_H(i)$ is used (see García-Risueño et al., J. Comp. Chem. 35, 427 (2014)). This method defines cells neighbouring cell $i$, which have volume $\Omega(i)/8$ (in 3D) and charge density obtained by interpolation. In the calculation of $V_H(i)$, in order to avoid double counting of charge, and to cancel part of the errors arising from considering the distances constant in the summation above, a term $-\alpha_{FMM}V_{self.int.}(i)$ is added to the summation (see the paper for the explicit formulae).

Name AnimationMultiFiles
Section Utilities::oct-xyz-anim
Type logical
Default false

If true, each iteration written will be in a separate file.

Name AnimationSampling
Section Utilities::oct-xyz-anim
Type integer
Default 100

Sampling rate of the animation. The animation will be constructed using the iteration numbers that are multiples of AnimationSampling.