# Frequency meshes

### This page gives hints on how to define frequency meshes (on the imaginary and real axes) for MBPT calculations with the ABINIT package.

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

Mentioned in topic_GW, topic_SelfEnergy, topic_Susceptibility, help_features#7.

### Table of content:

- 1. Introduction.
- 2. Related lesson(s) of the tutorial.
- 3. Related input variables.

### 1. Introduction.

In the contour deformation technique, and other cases, one has to define a set of frequencies on which different numerical operations will be performed (computation of susceptibility matrices, integration along the real+imaginary axes). In the present topic, the input variables connected to such definitions are gathered.
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### 2. Related lesson(s) of the tutorial.

- The second lesson on GW (GW2) deals with the computation of the quasi-particle band structure of Aluminum, in the GW approximation (so, much better than the Kohn-Sham LDA band structure) without using the plasmon-pole model.
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### 3. Related input variables.

Basic input variables:

... freqremax [FREQuencies along the Real axis MAXimum]
... freqremin [FREQuencies along the Real axis MINimum]
... nfreqim [Number of FREQuencies along the IMaginary axis]
... nfreqmidm [Nth FREQuency Moment of the Imaginary part of the Dielectric Matrix]
... nfreqre [Number of FREQuencies along the REal axis]

Input variables for experts:

... cd_customnimfrqs [Contour Deformation CUSTOM IMaginary FReQuencieS]
... cd_frqim_method [Contour Deformation FReQuency integration on IMaginary axis Method]
... cd_full_grid [Contour Deformation FULL GRID in complex plane]
... cd_halfway_freq [Contour Deformation tangent grid HALFWAY FREQuency]
... cd_imfrqs [Contour Deformation IMaginary FReQuencieS]
... cd_max_freq [Contour Deformation grid MAXimum FREQuency]
... cd_subset_freq [Contour Deformation grid calculate SUBSET of FREQuencies]
... gw_customnfreqsp [GW CUSTOM FREQuencies for SPectral function]
... gw_freqsp [GW SPectral FREQuencies]
... gw_frqim_inzgrid [GW Contour Deformation FReQuencies on IMaginary axis Inverse Z Grid]
... gw_frqre_inzgrid [GW Contour Deformation FReQuencies on REal axis Inverse Z Grid]
... gw_frqre_tangrid [GW Contour Deformation FReQencies on REal axis - Use Tangent Grid]
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