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| {{TAGDEF|IMIX|0 {{!}} 1 {{!}} 2 {{!}} 3 {{!}} 4|4}} | | {{TAGDEF|IMIX|0 {{!}} 1 {{!}} 2 {{!}} 4|4}} |
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| Description: {{TAG|IMIX}} specifies the type of mixing. | | Description: {{TAG|IMIX}} specifies the type of mixing. |
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| ::<math>\rho_{N+1}=\rho_{N+1}+\dot{\rho}_{N+1/2}</math>. | | ::<math>\rho_{N+1}=\rho_{N+1}+\dot{\rho}_{N+1/2}</math>. |
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| *{{TAG|IMIX}}=3
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| *{{TAG|IMIX}}=4 | | *{{TAG|IMIX}}=4 |
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Revision as of 17:11, 7 February 2011
IMIX = 0 | 1 | 2 | 4
Default: IMIX = 4
Description: IMIX specifies the type of mixing.
![\rho _{{{\rm {mix}}}}=\rho _{{{\rm {out}}}}](https://www.vasp.at/wiki/restbase/vasp.at/v1/media/math/render/svg/dedf6a6645933ea14bf93141ec89521e6628071d)
- The mixed density is given by
![\rho _{{{\rm {mix}}}}\left(G\right)=\rho _{{{\rm {in}}}}\left(G\right)+A{\frac {G^{2}}{G^{2}+B^{2}}}{\Bigl (}\rho _{{{\rm {out}}}}\left(G\right)-\rho _{{{\rm {in}}}}\left(G\right){\Bigr )}](https://www.vasp.at/wiki/restbase/vasp.at/v1/media/math/render/svg/db2065aed0113d1f690b7d222729e4e08270c672)
- with
=AMIX and
=BMIX
- If BMIX is chosen to be very small, e.g. BMIX=0.0001, a simple straight mixing is obtained. Please mind, that BMIX=0 might cause floating point exceptions on some platforms.
- IMIX=2: A variant of the popular Tchebycheff mixing scheme.[2]
- In our implementation a second order equation of motion is used, that reads:
![{\ddot {\rho }}_{{{\rm {in}}}}\left(G\right)=2*A{\frac {G^{2}}{G^{2}+B^{2}}}{\Bigl (}\rho _{{{\rm {out}}}}\left(G\right)-\rho _{{{\rm {in}}}}\left(G\right){\Bigr )}-\mu {\dot {\rho }}_{{{\rm {in}}}}\left(G\right)](https://www.vasp.at/wiki/restbase/vasp.at/v1/media/math/render/svg/abd58206cb20ee861190aeca0d0d968b7b43db6c)
- with
=AMIX,
=BMIX, and
=AMIN.
- A simple velocity Verlet algorithm is used to integrate this equation, and the discretized equation reads (the index N now refers to the electronic iteration, F is the force acting on the charge):
![{\dot {\rho }}_{{N+1/2}}={\Bigl (}\left(1-\mu /2\right){\dot {\rho }}_{{N-1/2}}+2*F_{N}{\Bigr )}/\left(1+\mu /2\right)](https://www.vasp.at/wiki/restbase/vasp.at/v1/media/math/render/svg/0d588c0dfe0ed3f135456fd8e536cc2ff4cf6a34)
- where
![F\left(G\right)=A{\frac {G^{2}}{G^{2}+B^{2}}}{\Bigl (}\rho _{{{\rm {out}}}}\left(G\right)-\rho _{{{\rm {in}}}}\left(G\right){\Bigr )}](https://www.vasp.at/wiki/restbase/vasp.at/v1/media/math/render/svg/ded6262d1c2df5eb20f7f50b0caf760afd1b15d2)
- and
.
Related Tags and Sections
INIMIX,
MAXMIX,
AMIX,
BMIX,
AMIX_MAG,
BMIX_MAG,
AMIN,
MIXPRE,
WC
References
Contents