[gmx-users] poor average exchange ratio for each replica

[YanhuaOuyang]

Dear Grimacs users,
I did use the equation:Ti=T0*ek*i  to generate a temperature distribution, after a 2-ns  REMD, I check the md.log file. I find the average exchange ratio for each replica is poor. the average exchange ratio is as below

Replica exchange statistics
Repl  499 attempts, 250 odd, 249 even
Repl  average probabilities:
Repl     0    1    2    3    4    5    6    7    8    9   10   11   12   13   14   15   16   17   18   19   20   21   22   23   24   25   26   27   28   29   30   31   32   33   34   35   36   37   38   39   40   41   42   43   44   45
Repl      .07  .08  .05  .05  .06  .06  .06  .06  .06  .05  .05  .04  .03  .05  .03  .03  .03  .01  .03  .02  .04  .02  .02  .02  .01  .02  .02  .01  .01  .01  .01  .01  .01  .01  .01  .02  .01  .01  .02  .00  .02  .00  .02  .02  .01

Repl  number of exchanges:
Repl     0    1    2    3    4    5    6    7    8    9   10   11   12   13   14   15   16   17   18   19   20   21   22   23   24   25   26   27   28   29   30   31   32   33   34   35   36   37   38   39   40   41   42   43   44   45
Repl       14   20   13   12   16   14   15   17   14   15    9   12    8   13    7    5    7    2    5    6   10    6    4    6    2    5    3    1    6    3    3    3    2    3    4    5    2    3    4    2    4    2    4    4    3

 the temperature distribution: 270.00 272.84 275.77 278.79 281.91 285.12 288.43 291.84 295.36 299.00 302.75 306.61 310.60 314.72 318.97 323.36 327.89 332.56 337.39 342.38 347.52 352.83 358.32 363.98 369.82 375.86 382.09 388.51 395.15 401.99 409.05 416.33 423.84 431.59 439.58 447.81 456.29 465.04 474.05 483.34 492.92 502.78 512.96 523.45 534.28 545.46.

the temperature is reasonable, but the acceptance ratio is far from 0.2-0.3. So I get a another temperature distribution with the website:http://origami.phys.rpi.edu/racc/rate_of_acceptance.php <http://origami.phys.rpi.edu/racc/rate_of_acceptance.php>  ,the average exchange ratio still is  less than 0.05. 
I really do not know how to improve the situation. What should I do in the next step? How should I improve such a low exchange ratio?

best regards,
Ouyang