<div dir="ltr"><p class="separator" style="text-align: center; clear: both;"> </p>Dear all,<div>I'm encountering convergence problem for the MD simulation of single molecule adsorption on Ni surface. This is a test case to see if I can calculate my desired system. I'm using a GLE thermostat. </div><div>I've tried using DFTB and PM6 but in both cases I receive the error below, mentioning: </div><div><b>"Bad condition number R_COND = 0.000E+00 (smaller than the machine working precision" common/mathlib.F:709.</b></div><div>As you know, DFTB or PM6 are chosen because of their inexpensiveness! <b><br></b></div><div><br></div><p class="separator" style="text-align: center; clear: both;"><img src="cid:b596ac92-eb82-474c-b449-b680c7082cca" alt="Capture.PNG" style="margin-left: 1em; margin-right: 1em;" width="400" height="293"><br></p><p class="separator" style="text-align: left; clear: both;"><br></p><p class="separator" style="text-align: left; clear: both;">Here is my input file and I've attached the coordinate file:</p><p class="separator" style="text-align: left; clear: both;"><br></p><p class="MsoPlainText"><span style="font-family:"Courier New"">&GLOBAL<br>
PROJECT CH4-Ni<br>
RUN_TYPE MD<br>
PRINT_LEVEL LOW<br>
&END GLOBAL<br>
<br>
&FORCE_EVAL<br>
METHOD Quickstep<br>
&DFT<br>
&QS<br>
METHOD PM6<br>
&SE<br>
RC_INTERACTION [angstrom]
8.0<br>
RC_COULOMB [angstrom] 8.0<br>
RC_RANGE [angstrom] 0.05<br>
&END<br>
&END QS<br>
! &QS<br>
!
METHOD DFTB<br>
!
&DFTB<br>
!
SELF_CONSISTENT T<br>
!
DO_EWALD T<br>
!
DISPERSION T<br>
!
&PARAMETER<br>
!
PARAM_FILE_PATH
/data/scc<br>
!
PARAM_FILE_NAME
scc_parameter<br>
!
UFF_FORCE_FIELD uff_table<br>
!
&END PARAMETER<br>
!
&END DFTB<br>
! &END QS<br>
&SCF<br>
MAX_SCF 30<br>
EPS_SCF
5.0E-6<br>
&OUTER_SCF<br>
MAX_SCF
30<br>
EPS_SCF
5.0E-6<br>
&END<br>
&DIAGONALIZATION ON<br>
ALGORITHM
STANDARD<br>
&END
DIAGONALIZATION<br>
ADDED_MOS
300<br>
&SMEAR ON<br>
METHOD
FERMI_DIRAC<br>
ELECTRONIC_TEMPERATURE [K] 350<br>
&END
SMEAR<br>
&MIXING<br>
METHOD
BROYDEN_MIXING<br>
BETA
1.5<br>
ALPHA 0.1<br>
NBROYDEN 8<br>
&END
MIXING<br>
&PRINT<br>
&RESTART LOW<br>
BACKUP_COPIES 1<br>
&END
RESTART<br>
&END
PRINT<br>
SCF_GUESS
ATOMIC<br>
&END SCF <br>
&POISSON<br>
POISSON_SOLVER
MT<br>
PERIODIC XY<br>
&EWALD<br>
EWALD_TYPE SPME<br>
GMAX 25<br>
O_SPLINE 5<br>
&END EWALD<br>
&END POISSON<br>
&END DFT<br>
<br>
&SUBSYS<br>
&CELL<br>
ABC 12.4597
12.9485 23.1387<br>
PERIODIC XY<br>
&END CELL<br>
&COORD<br>
@INCLUDE 'ch4-ni.coord'<br>
&END COORD<br>
&TOPOLOGY<br>
&CENTER_COORDINATES<br>
&END
CENTER_COORDINATES<br>
&END TOPOLOGY<br>
&END SUBSYS<br>
&END FORCE_EVAL<br>
<br>
&MOTION<br>
&MD<br>
ENSEMBLE NVT<br>
STEPS 10000<br>
TIMESTEP 0.5<br>
TEMPERATURE 300<br>
&THERMOSTAT<br>
REGION
MASSIVE<br>
TYPE GLE<br>
&GLE<br>
NDIM
3<br>
A_SCALE
[ps^-1] 1.00<br>
A_LIST 2.000000000000e+0 1.365763041717e+1 0.000000000000e+0<br>
A_LIST -1.365763041717e+1 9.418257899376e-1 5.860040064992e+2<br>
A_LIST 0.000000000000e+0 -5.860040064992e+2 0.000000000000e+0<br>
C_LIST 3.071856358605e+2 1.052252204958e+0 -3.083120039764e+2<br>
C_LIST 1.052252204958e+0 1.353606645969e+4 0.000000000000e+0<br>
C_LIST -3.083120039764e+2 0.000000000000e+0 1.352888082383e+4<br>
&END
GLE<br>
&END THERMOSTAT<br>
&PRINT<br>
&ENERGY<br>
&EACH<br>
MD 10<br>
&END EACH<br>
&END
ENERGY<br>
&END PRINT<br>
&END MD<br>
&FREE_ENERGY<br>
&FREE_ENERGY_INFO<br>
&EACH<br>
MD
1000<br>
&END<br>
&END<br>
&METADYN<br>
&PRINT<br>
&COLVAR<br>
COMMON_ITERATION_LEVELS 3<br>
&EACH<br>
MD 1<br>
&END<br>
&END<br>
&HILLS<br>
COMMON_ITERATION_LEVELS 3<br>
&EACH<br>
MD 1<br>
&END<br>
&END<br>
&END<br>
&END METADYN<br>
&END FREE_ENERGY<br>
&PRINT<br>
&TRAJECTORY<br>
FORMAT XYZ<br>
&EACH<br>
MD
20<br>
&END
EACH<br>
&END TRAJECTORY<br>
&RESTART_HISTORY<br>
&EACH<br>
MD 10000<br>
&END
EACH<br>
&END
RESTART_HISTORY<br>
&RESTART OFF<br>
&END RESTART<br>
&END PRINT<br>
&END MOTION<br></span><br>I would be grateful if anyone could take a look to my input file and let me know about the possible way to get the structure converged. I've already relaxed the metal structure before using it for md simulation. <span style="font-family:"Courier New""><br>
<o:p> </o:p></span></p><div>Thanks in advance.</div><div><br></div><div>Amin</div></div>