RenĂ© van Bevern has a solution for using Computer Modern for

`\mathcal`

and `\sum`

along with the `mathptmx`

package.Using his idea, I have a very similar solution for using the Latin Modern font family instead.

```
\SetMathAlphabet{\mathcal}{normal}{OMS}{lmsy}{m}{n}
\SetMathAlphabet{\mathcal}{bold}{OMS}{lmsy}{m}{n}
\SetSymbolFont{largesymbols}{normal}{OMX}{lmex}{m}{n}
\SetSymbolFont{largesymbols}{bold}{OMX}{lmex}{m}{n}
```