# Some artificial modifications of the physics - modify nuclear or electronic masses, chemical potential ...

### This page gives hints on how to perform some artificial modifications of the physics with the ABINIT package.

##### Copyright (C) 2016-2017 ABINIT group (XG)

Mentioned in help_features#2.5.

### Table of content:

- 1. Introduction.
- 2. Related input variables.
- 3. Selected input files.

### 1. Introduction.

With a computer, one can consider non-physical modifications of the system to help the understanding the physics ...

The nuclear masses and free electron mass can be modified. A fake space dependent chemical potenial can be added, see chempot, as well as the electrostatic potential of a slab, jellslab. A simple sine/cosine potential with a wavevector compatible with the (super)call can also be added, see qprtrb.
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### 2. Related input variables.

Basic input variables:

... amu [Atomic Mass Units]

Useful input variables:

... qprtrb [Q-wavevector of the PERTurbation]
... vprtrb [potential -V- for the PeRTuRBation]

Input variables for experts:

... chempot [spatially varying CHEMical POTential]
... effmass_free [EFFective MASS for the FREE electron]
... jellslab [include a JELLium SLAB in the cell]
... nzchempot [Number of Z reduced coordinates that define the spatial CHEMical POTential]
... slabwsrad [jellium SLAB Wigner-Seitz RADius]
... slabzbeg [jellium SLAB BEGinning edge along the Z direction]
... slabzend [jellium SLAB ENDing edge along the Z direction]
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### 3. Selected input files.

WARNING : as of ABINITv8.6.x, the list of input files provided in the specific section of the topics Web pages is still to be reviewed/tuned. In some cases, it will be adequate, and in other cases, it might be incomplete, or perhaps even useless.
The user can find some related example input files in the ABINIT package in the directory /tests, or on the Web:

tests/v1/Input: t25.in
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