MD melting problem

[Matt W]

Probably unrelated to you actual question, but changing to

STRESS_TENSOR DIAGONAL_ANALYTICAL

should give you a big speed up.

Matt

On Thursday, May 3, 2018 at 1:37:55 AM UTC+1, 498... at qq.com wrote:
>
> Hello, everyone, I want to simulate the melting structure of molten salts. 
> The simulation began with  crystal structure and temperature was set at 
> 3000 K in NPT ensemble， which is far more higher than the melting point. 
> However, the result is frustrating. After 100 ps runs, the ions still in 
> crystal structure. The parameters in the force field is in published paper 
> and widely used, so I wonder somewhere in the input file is wrong. The file 
> is listed below, could anyone tell me the possible problems? Thanks very 
> much.
>
>
> &GLOBAL                         ! Section with general information 
> regarding which kind of simulation to perform an parameters for the whole 
> PROGRAM
>   PROJECT C6                    ! Name of the project. This word will 
> appear as part of a name of all ouput files (except main ouput file, 
> specified with -o option)
>   RUN_TYPE MD           ! Molecular Dynamics
>   PRINT_LEVEL low
> &END GLOBAL
>
>
> &FORCE_EVAL ! This section defines method for calculating energy and 
> forces
>   METHOD FIST ! Using Molecular Mechanics
>   STRESS_TENSOR NUMERICAL
>   &MM
>     &FORCEFIELD ! This section specifies forcefield parameters
>       ..........
>     &END FORCEFIELD
>     &POISSON ! This section specifies parameters for the Poisson solver
>       &EWALD ! This section specifies parameters for the EWALD summation 
> method (for the electrostatics)
>         EWALD_TYPE none ! Standard real-space coulomb potential is 
> computed together with the non-bonded contributions.
>       &END EWALD
>     &END POISSON
> &NEIGHBOR_LISTS
>   GEO_CHECK TRUE
>   NEIGHBOR_LISTS_FROM_SCRATCH TRUE
>   VERLET_SKIN 1
>     &END NEIGHBOR_LISTS 
>   &END MM
>   &SUBSYS ! This section defines the system
>     &CELL ! Unit cell set up
>       ABC 22.56 22.56 22.56 ! Lengths of the cell vectors A, B, and C
>       ALPHA_BETA_GAMMA 90.0 90.0 90.0
>       PERIODIC  XYZ
>     &END CELL
>     &TOPOLOGY 
>      COORD_FILE_NAME  NaCl.xyz 
>      COORDINATE xyz ! The type of the file  is XYZ
>     &END TOPOLOGY
>   &END SUBSYS
> &END FORCE_EVAL
>
> &MOTION ! This section defines a set of tool connected with the motion of 
> the nuclei.
>  &PRINT
>  &TRAJECTORY
>     LOG_PRINT_KEY T
>     FORMAT XMOL
>     &EACH
>      MD 10000
>     &END EACH
>     ADD_LAST NUMERIC   
>  &END TRAJECTORY
>  &END PRINT
>  &MD 
>     ENSEMBLE NPT_I
>     TEMPERATURE 3000
> &BAROSTAT
>   PRESSURE 0
>   TEMPERATURE 3000
> &END BAROSTAT
> &THERMOSTAT
>         TYPE NOSE
>          REGION GLOBAL
>          &NOSE
>            TIMECON 100
>            LENGTH 3
>            MTS 2
>          &END NOSE
>      &END THERMOSTAT
> TIMESTEP 1.0
> STEPS 100000
>  &END MD
>
>   &PRINT
>     &RESTART
>       LOG_PRINT_KEY T
>       &EACH
>         MD 10000
>       &END EACH
>       ADD_LAST NUMERIC
>     &END RESTART
>   &END PRINT
> &END MOTION
>  &END
> &END MOTION
>
>
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