[CP2K:10259] MD melting problem

[jie wu]

Hello, Josip, this answer is really helpful. But I found the force field 
parameters in publication paper and the force field code has already been 
opened in their website. I tried to repeated the simulation in the paper 
with the exact parameters and sets. In the paper, the authors sasid:"all 
works conducted in NVT ensemble, at three different temperatures within an 
interval of 100 K. Starting from crystal structure, after equilibration for 
100 ps to reach the molten state, a series of 250ps production runs 
performed at each temperature, until converged statistical averages could 
be obtained for the transport coefficients. " Maybe I should email the 
author to check what I missed. What's more, though the code in public is 
the code of CP2K input, the authors conducted simulations with CPMD in the 
paper. Is there any concerns with the sorftware difference?

在 2018年5月3日星期四 UTC+8下午9:46:26，Josip Lovrić写道：
>
> Maybe wise thing to do is to check force field first, maybe you have some 
> mistake in definition of force field.
> Try to take just few atoms and check how energy evolves. If the potential 
> is wrong you will get strange values.
>
> Josip
>
> 2018-05-03 14:12 GMT+02:00 <498... at qq.com <javascript:>>:
>
>> 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>:
>>>
>>>> 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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>
>
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