[CP2K:10253] MD melting problem

[4985... at qq.com]

Hello, Josip, thanks very much for the answer. The system is bulk. 10s is 
too long to simulate, maybe build the initial configuration based on the 
experimental density in random way is a good choice. However, I also 
encountered a problem in that way, the pre-equilibriumed system is a little 
larger than the experimental density evaluated volume. So in avoid to the 
error of 'GEOMETRY wrong or EMAX_SPLINE too small!', I set the cell abc 
accoording to  the pre-equilibriumed volume. With the time accumulating, I 
found the volume expanded in NVT ensemble which is ridiculous and holes 
began to form in the bulk. I don't know what caused this.

在 2018年5月3日星期四 UTC+8下午3:33:29，Josip Lovrić写道：
>
> Normaly, phase transitions are hard to reproduce. You are not first one to 
> be frustrated. Secondly 100 ps is way to short, you need to go at least to 
> 10s of ns and maybe if you are lucky you will see some melting. Also, do 
> you have slab or bulk?
>
> Josip
> Greetings from Gothenburg
>
> 2018-05-03 2:37 GMT+02:00 <498... at qq.com <javascript:>>:
>
>> Hello, everyone, I recently want simulated the melting structure of 
>> molten salts. The simulation begin with the crystal structure and intend to 
>> be melt at 3000 K in NPT ensemble， but 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 maybe I write 
>> something of the input wrong. The input file is listed below, pls help out 
>> the dilemma, 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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>
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