drastic change in pressure on changing smoothing

Matt W MattWa... at gmail.com
Fri Dec 4 12:01:48 UTC 2015


Hi,

running NPT calculations are not straightforward. The stress tensor needs 
to be reasonably converged wrt the cutoff to get reliable results. The 
cutoff to converge the stress tensor might be much larger than for reliable 
forces.

Matt

On Thursday, December 3, 2015 at 5:00:18 PM UTC, Bernd Ensing wrote:
>
>
> Dear cp2k developers,
>
> Is it known whether there is a bug in the calculation of the pressure 
> tensor when using XC_SMOOTH_RHO NN10?
> Using this smoothing option results in very negative pressures for a 
> typical system containing 64 water molecules (see message below of Ambuj 
> Tiwari).
> Does this strange behaviour also affect the forces on the atoms in general?
>
> Many thanks in advance for your comments.
> best wishes,
>
> Bernd Ensing
>
>
>
> Op woensdag 25 november 2015 13:49:36 UTC+1 schreef Ambuj Tiwari:
>>
>> Dear All,
>> I am running a NVT MD simulation on bulkwater(64 water molecules) . The 
>> problem is related to pressure calculation. 
>> I was calculating the pressure for the system and found highly negative 
>> values(in order of -25000) and then I switched all the parameters one by 
>> one and eventually found out that on changing smoothing from XC_SMOOTH_RHO 
>> NN10 to USE_FINER_GRID it came down to less negative values(-5000). Is this 
>> some kind of bug in the program or more fundamental problem.
>>
>> I am attaching the input file and bottom of .ener .stress file here.
>>
>> Regards,
>> Ambuj
>>
>>
>> *'input file 1'*
>>
>> <https://en.wikipedia.org/wiki/Car%E2%80%93Parrinello_molecular_dynamics#cite_note-3>
>>     &XC
>>       &XC_FUNCTIONAL BLYP
>>       &END XC_FUNCTIONAL
>>       &VDW_POTENTIAL
>>         DISPERSION_FUNCTIONAL PAIR_POTENTIAL
>>          &PAIR_POTENTIAL
>>             TYPE DFTD3
>>             PARAMETER_FILE_NAME /home/ensing/BASIS_SET/dftd3.dat
>>             REFERENCE_FUNCTIONAL BLYP
>>          &END PAIR_POTENTIAL
>>       &END VDW_POTENTIAL
>>       &XC_GRID
>>   
>> *       XC_SMOOTH_RHO NN10         XC_DERIV SPLINE2_SMOOTH*
>>       &END XC_GRID
>>     &END XC
>>
>> *'input file 2'*
>>                                                                                                                                                                                                                                                                            
>>
>>    &XC
>>       &XC_FUNCTIONAL BLYP
>>       &END XC_FUNCTIONAL
>>       &VDW_POTENTIAL
>>         DISPERSION_FUNCTIONAL PAIR_POTENTIAL
>>          &PAIR_POTENTIAL
>>             TYPE DFTD3
>>             PARAMETER_FILE_NAME /home/ensing/BASIS_SET/dftd3.dat
>>             REFERENCE_FUNCTIONAL BLYP
>>          &END PAIR_POTENTIAL
>>       &END VDW_POTENTIAL
>>       &XC_GRID
>> *      USE_FINER_GRID *
>>       &END XC_GRID
>>     &END XC
>>
>>
>> *'*.ener 1'*
>>  
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> *    163298        81649.000000         0.295424393       
>> 325.610938118     -1101.039478079     -1100.781654417        
>> 22.112000000    163299        81649.500000         0.294462120       
>> 324.550339188     -1101.039370784     -1100.781669902        
>> 22.078000000    163300        81650.000000         0.294961268       
>> 325.100490947     -1101.040473093     -1100.781725319        
>> 25.159000000    163301        81650.500000         0.296162908       
>> 326.424914893     -1101.042161493     -1100.781750771        
>> 22.115700000    163302        81651.000000         0.298814382       
>> 329.347317264     -1101.044236790     -1100.781694623        
>> 22.139200000    163303        81651.500000         0.301128239       
>> 331.897603891     -1101.047561646     -1100.781602129        
>> 24.739700000    163304        81652.000000         0.307044448       
>> 338.418332848     -1101.053434140     -1100.781587012        
>> 24.682400000    163305        81652.500000         0.316425516       
>> 348.757961573     -1101.061982016     -1100.781699977        
>> 22.044200000    163306        81653.000000         0.327014965       
>> 360.429442967     -1101.071396202     -1100.781872287        22.101900000*
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> *'*.ener 2'        91           45.500000         0.316250053       
>> 348.564569099     -1102.663360533     -1102.332927916        
>> 65.288200000        92           46.000000         0.315037265       
>> 347.227857880     -1102.661696314     -1102.332913105        
>> 65.190400000        93           46.500000         0.314019534       
>> 346.106135819     -1102.660798344     -1102.332914267        
>> 65.276700000        94           47.000000         0.314010873       
>> 346.096588928     -1102.660760313     -1102.332937169        
>> 65.315200000        95           47.500000         0.315000947       
>> 347.187829574     -1102.661384548     -1102.332972600        
>> 65.163300000        96           48.000000         0.315886554       
>> 348.163928325     -1102.662099658     -1102.333054612        
>> 65.248800000        97           48.500000         0.315298803       
>> 347.516120600     -1102.661788013     -1102.333132240        
>> 65.120100000        98           49.000000         0.313543746       
>> 345.581730970     -1102.659461626     -1102.333136220        
>> 65.202000000        99           49.500000         0.309178417       
>> 340.770351269     -1102.655147713     -1102.333068024        
>> 63.328600000       100           50.000000         0.304077471       
>> 335.148189283     -1102.649908792     -1102.332978856        
>> 64.191200000                                                                                                                                                                                                                                                                    
>> '*.stress 1'*
>>     163294   81647.000   -23587.6933211956     2342.2050511699    
>> -2620.1253216644     2342.2050511699   -23228.0050606190     
>> 3414.1775796133    -2620.1253216644     3414.1775796133   -20169.0313283565
>>   163295   81647.500   -22389.3419955310     1849.7028598497    
>> -2508.5434330934     1849.7028598497   -24356.6599768539     
>> 2800.7048436858    -2508.5434330934     2800.7048436858   -22725.6161101663
>>   163296   81648.000   -21214.9735696668     1148.0699336617    
>> -2218.3871712667     1148.0699336617   -25144.9624318558     
>> 1975.3590510643    -2218.3871712667     1975.3590510643   -24795.3384458679
>>   163297   81648.500   -20309.0216433928      302.8654094409    
>> -1803.1704603762      302.8654094409   -25394.9473522949      
>> 996.8049404043    -1803.1704603762      996.8049404043   -26162.6367896449
>>   163298   81649.000   -19855.8176878975     -598.7972734722    
>> -1300.5824885129     -598.7972734722   -24999.8852946563      
>> -79.5868061270    -1300.5824885129      -79.5868061270   -26686.2571452786
>>   163299   81649.500   -19956.2226579495    -1461.2946422884     
>> -742.0897491587    -1461.2946422884   -24019.8747323228    
>> -1206.1348202948     -742.0897491587    -1206.1348202948   -26376.7375359960
>>   163300   81650.000   -20534.1679738551    -2200.5578986806     
>> -164.8658164621    -2200.5578986806   -22584.1267162156    
>> -2322.5467222548     -164.8658164621    -2322.5467222548   -25268.9877352706
>>   163301   81650.500   -21452.3785466678    -2746.9001879179      
>> 376.2080784084    -2746.9001879179   -20951.8376784856    
>> -3338.3737161118      376.2080784084    -3338.3737161118   -23492.0302819538
>>
>>
>> *'*.stress 2'*
>>       83      41.500    14620.6789775920     1631.8725215074     
>> 2233.0775150043     1631.8725215074     6922.5364171994     
>> 1568.9298877547     2233.0775150043     1568.9298877547     4863.0813795099
>>       84      42.000    13465.9504463874     1646.6798565162     
>> 1742.3968878509     1646.6798565162     7528.7642280447     
>> 1356.1689695128     1742.3968878509     1356.1689695128     3678.0979512013
>>       85      42.500    11929.6829243335     1557.1878823967     
>> 1189.8285351507     1557.1878823967     7536.6702267556      
>> 906.2538614813     1189.8285351507      906.2538614813     2706.1024195638
>>       86      43.000    10242.7023865733     1377.0907756499      
>> 607.2431768383     1377.0907756499     6953.6306436901      
>> 280.8453243292      607.2431768383      280.8453243292     2111.5249630222
>>       87      43.500     8704.9333307887     1111.3766575987       
>> 27.5775490784     1111.3766575987     5939.0119410377     
>> -388.5800033232       27.5775490784     -388.5800033232     2026.3208988151
>>       88      44.000     7481.3245836153      770.0630298266     
>> -494.3356330308      770.0630298266     4626.9158749281     
>> -951.4354212867     -494.3356330308     -951.4354212867     2390.6634657579
>>       89      44.500     6663.8847520724      360.1790480556     
>> -890.4213349779      360.1790480556     3225.2634082928    
>> -1279.9170414956     -890.4213349779    -1279.9170414956     3064.5349399335
>>       90      45.000     6254.7640395386     -100.7086327357    
>> -1091.1835737339     -100.7086327357     1954.1849838233    
>> -1309.6032354774    -1091.1835737339    -1309.6032354774     3839.7803365830
>>       91      45.500     6155.5011736691     -574.1695321638    
>> -1051.6467240489     -574.1695321638      957.4978282879    
>> -1053.9528084102    -1051.6467240489    -1053.9528084102     4443.4869908843
>>       92      46.000     6285.5912946027    -1016.5428590808     
>> -783.4044479712    -1016.5428590808      376.4627244754     
>> -574.9649194818     -783.4044479712     -574.9649194818     4722.8910330993
>>       93      46.500     6504.7623119346    -1380.8418795540     
>> -361.7805767782    -1380.8418795540      216.2588001339       
>> 37.9199806709     -361.7805767782       37.9199806709     4578.5854391507
>>       94      47.000     6695.7329680208    -1630.3118660115       
>> 95.8727981760    -1630.3118660115      437.0880477724      
>> 702.9749077441       95.8727981760      702.9749077441     4059.5915440691
>>
>>
>> Thanks in advance!
>>
>
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