How EAM potential files for Cu-Ni alloy are calculated?

Hi all,

I looked into original paper,S.M. Foiles, Phys. Rev. B 32, 7685 (1985), cited by Cu_smf7.eam and Ni_smf7.eam potential files and found the effective charge equation, Z®=Z0e^(-alphaR), where Z0=11, alpha=1.513 and R is the separation between atoms. However, the Z® values calculated are different from values listed in Cu_smf7.eam file. Also, I’ve tried another effective charge equation, Z®=Z0(1+betaR^v)e^(-alpha*R), reported by S. M. Foiles, M. I. Baskes, and M. S. Daw, Phys. Rev. B 33, 7983 (1986), but it still not even close with R above 4 Angstrom.

Especially the last number for Z® is set to the order of magnitude of -16 seems not obey the function since the previous number is at the order of magnitude of -5 in Cu_smf7.eam.

The following are numbers I’ve obtained using the exponential function:

11 10.81379 10.63107 10.45177 10.27581 10.10314 9.933686 9.767382 9.604165 9.443973 9.286746 9.132425 8.980951 8.832267 8.686317 8.543047 8.402404 8.264334 8.128787 7.995713 7.865062 7.736786 7.610838 7.487172 7.365744 7.246507 7.129421 7.014441 6.901526 6.790637 6.681732 6.574773 6.469723 6.366543 6.265197 6.165649 6.067864 5.971807 5.877446 5.784747 5.693677 5.604206 5.516302 5.429936 5.345076 5.261695 5.179763 5.099253 5.020138 4.942391 4.865985 4.790896 4.717097 4.644565 4.573274 4.503202 4.434326 4.366622 4.300069 4.234645 4.170328 4.107098 4.044933 3.983816 3.923724 3.86464 3.806545 3.749419 3.693246 3.638007 3.583684 3.530262 3.477723 3.426051 3.37523 3.325244 3.276078 3.227717 3.180147 3.133351 3.087318 3.042032 2.99748 2.953649 2.910526 2.868097 2.826351 2.785275 2.744857 2.705085 2.665947 2.627433 2.589531 2.55223 2.51552 2.479389 2.443829 2.408827 2.374376 2.340465 2.307084 2.274225 2.241878 2.210033 2.178684 2.14782 2.117433 2.087516 2.058059 2.029056 2.000497 1.972376 1.944685 1.917417 1.890564 1.86412 1.838077 1.812428 1.787167 1.762288 1.737783 1.713647 1.689873 1.666455 1.643388 1.620665 1.598281 1.57623 1.554506 1.533104 1.512019 1.491246 1.470779 1.450613 1.430744 1.411166 1.391875 1.372866 1.354135 1.335676 1.317487 1.299561 1.281896 1.264486 1.247328 1.230417 1.213751 1.197324 1.181133 1.165174 1.149444 1.133939 1.118655 1.103589 1.088738 1.074097 1.059664 1.045436 1.03141 1.017581 1.003948 0.990506 0.977254 0.964188 0.951306 0.938603 0.926079 0.91373 0.901553 0.889546 0.877705 0.86603 0.854516 0.843163 0.831966 0.820924 0.810035 0.799296 0.788705 0.77826 0.767959 0.757799 0.747778 0.737895 0.728146 0.718532 0.709048 0.699694 0.690467 0.681366 0.672388 0.663533 0.654797 0.64618 0.63768 0.629294 0.621022 0.612862 0.604812 0.59687 0.589035 0.581305 0.57368 0.566157 0.558734 0.551411 0.544186 0.537058 0.530025 0.523086 0.51624 0.509485 0.50282 0.496243 0.489755 0.483352 0.477035 0.470801 0.46465 0.45858 0.452591 0.446682 0.44085 0.435095 0.429417 0.423813 0.418284 0.412827 0.407442 0.402129 0.396885 0.39171 0.386603 0.381563 0.376589 0.371681 0.366837 0.362057 0.357339 0.352683 0.348088 0.343553 0.339077 0.33466 0.330301 0.325998 0.321752 0.317561 0.313425 0.309343 0.305314 0.301338 0.297413 0.293539 0.289716 0.285943 0.282218 0.278542 0.274914 0.271333 0.267799 0.26431 0.260867 0.257468 0.254114 0.250803 0.247535 0.244309 0.241125 0.237983 0.234881 0.231819 0.228797 0.225815 0.22287 0.219964 0.217096 0.214264 0.21147 0.208711 0.205988 0.2033 0.200647 0.198029 0.195444 0.192893 0.190374 0.187888 0.185435 0.183013 0.180622 0.178262 0.175933 0.173633 0.171364 0.169124 0.166912 0.164729 0.162575 0.160448 0.158349 0.156277 0.154231 0.152212 0.150219 0.148252 0.14631 0.144394 0.142502 0.140634 0.138791 0.136971 0.135175 0.133402 0.131652 0.129925 0.128219 0.126536 0.124875 0.123235 0.121617 0.120019 0.118442 0.116885 0.115348 0.113832 0.112335 0.110857 0.109398 0.107958 0.106537 0.105134 0.10375 0.102383 0.101034 0.099702 0.098388 0.097091 0.09581 0.094546 0.093299 0.092067 0.090852 0.089652 0.088468 0.087299 0.086145 0.085007 0.083883 0.082773 0.081678 0.080598 0.079531 0.078478 0.077439 0.076413 0.075401 0.074401 0.073415 0.072442 0.071481 0.070533 0.069597 0.068673 0.067761 0.066861 0.065973 0.065096 0.064231 0.063377 0.062534 0.061702 0.060881 0.060071 0.059271 0.058482 0.057703 0.056934 0.056175 0.055426 0.054687 0.053958 0.053238 0.052527 0.051826 0.051134 0.050451 0.049776 0.049111 0.048455 0.047807 0.047167 0.046536 0.045913 0.045298 0.044692 0.044093 0.043502 0.042919 0.042344 0.041776 0.041215 0.040662 0.040117 0.039578 0.039046 0.038522 0.038004 0.037493 0.036989 0.036492 0.036001 0.035516 0.035038 0.034566 0.034101 0.033641 0.033188 0.03274 0.032299 0.031863 0.031433 0.031009 0.03059 0.030177 0.02977 0.029368 0.028971 0.028579 0.028192 0.027811 0.027435 0.027063 0.026697 0.026335 0.025979 0.025627 0.025279 0.024936 0.024598 0.024265 0.023935 0.02361 0.02329 0.022973 0.022661 0.022353 0.022049 0.02175 0.021454 0.021162 0.020874 0.02059 0.020309 0.020033 0.01976 0.01949 0.019225 0.018963 0.018704 0.018449 0.018197 0.017948 0.017703 0.017462 0.017223 0.016988 0.016755 0.016526 0.0163 0.016077 0.015857 0.01564 0.015426 0.015214 0.015006 0.0148 0.014597 0.014397 0.0142 0.014005 0.013813 0.013623 0.013436 0.013251 0.013069 0.01289 0.012712 0.012538 0.012365 0.012195 0.012027 0.011861 0.011698 0.011537 0.011378 0.011221 0.011067 0.010914 0.010763 0.010615

Could somebody explain how Cu_smf7.eam in lammps is obtained or how can I achieve reasonable values myself?

Thanks!

Best,
Jing

In src/pair_eam.cpp in this section of code:

  // create a z2r array for each file against other files, only for I >= J
  // interpolate zri and zrj to a single grid and cutoff

is a line that does some unit conversion, as well as converision
from a sqrt() form from the values in the file to what LAMMPS
uses:

z2r[n][m] = 27.2*0.529 * zri*zrj;

The files, as LAMMPS reads them, are in a standard DNYAMO format
which has been around for 30 years. You can try contacting Stephen
Foiles if you have further questions: foiles at sandia.gov.

Steve